SOCS (suppressors of cytokine signaling) box. The SOCS box is found in the C-terminal region of CIS/SOCS family proteins (in combination with a SH2 domain), ASBs (ankyrin repeat-containing proteins with a SOCS box), SSBs (SPRY domain-containing proteins with a SOCS box), and WSBs (WD40 repeat-containing proteins with a SOCS box), as well as, other miscellaneous proteins. The function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|
gi 1039732729 158 TSAPTLQHFCRLAINKCTGTIWGLPLPTRLKDYLEEYKFQ 197
Cdd:cd03736     1 TSTPSLQHLCRITINKCTRQIQELPLPTRLKDYLTEYTYH 40

Src homology 2 domains; Src homology 2 domains bind phosphotyrosine-containing polypeptides via 2 surface pockets. Specificity is provided via interaction with residues that are distinct from the phosphotyrosine. Only a single occurrence of a SH2 domain has been found in S. cerevisiae.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729   48 WYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIE-YQDGKFRLDSiicvkskLKQFDSVVHLI 126
Cdd:smart00252   3 WYHGFISREEAEKLLKNEGDGDFLVRDSESSPGDYVLSVRVKGKVKHYRIRrNEDGKFYLEG-------GRKFPSLVELV 75

                   ....*
gi 1039732729  127 DYYVQ 131
Cdd:smart00252  76 EHYQK 80

SH2 domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEA-PEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQD--GKFRLDSiicvksklKQFDSVVH 124
Cdd:pfam00017   1 WYHGKISRQEAERLLLNGkPDGTFLVRESESTPGGYTLSVRDDGKVKHYKIQSTDngGYYISGG--------VKFSSLAE 72

                  ....*
gi 1039732729 125 LIDYY 129
Cdd:pfam00017  73 LVEHY 77

SOCS box; The SOCS box acts as a bridge between specific substrate- binding domains and more generic proteins that comprise a large family of E3 ubiquitin protein ligases.

                          10        20        30
                  ....*....|....*....|....*....|....*.
gi 1039732729 161 PTLQHFCRLAINKCTGT-----IWGLPLPTRLKDYL 191
Cdd:pfam07525   3 RSLQHLCRLAIRRALGKrrlgaIDKLPLPPLLKDYL 38

Src homology 2 (SH2) domain found in cytokine-inducible SH2-containing protein (CIS); CIS family members are known to be cytokine-inducible negative regulators of cytokine signaling. The expression of the CIS gene can be induced by IL2, IL3, GM-CSF and EPO in hematopoietic cells. Proteasome-mediated degradation of this protein has been shown to be involved in the inactivation of the erythropoietin receptor. Suppressor of cytokine signalling (SOCS) was first recognized as a group of cytokine-inducible SH2 (CIS) domain proteins comprising eight family members in human (CIS and SOCS1-SOCS7). In addition to the SH2 domain, SOCS proteins have a variable N-terminal domain and a conserved SOCS box in the C-terminal domain. SOCS proteins bind to a substrate via their SH2 domain. The prototypical members, CIS and SOCS1-SOCS3, have been shown to regulate growth hormone signaling in vitro and in a classic negative feedback response compete for binding at phosphotyrosine sites in JAK kinase and receptor pathways to displace effector proteins and target bound receptors for proteasomal degradation. Loss of SOCS activity results in excessive cytokine signaling associated with a variety of hematopoietic, autoimmune, and inflammatory diseases and certain cancers. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  43 LSQTGWYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLDSIICVKSKLKQFDSV 122
Cdd:cd10718     1 LRESGWYWGSITASEAHQALQKAPEGTFLVRDSSHPSYMLTLSVKTTRGPTNVRIEYSDGSFRLDSSSLARPRLLSFPDV 80

                  ....*...
gi 1039732729 123 VHLIDYYV 130
Cdd:cd10718    81 VSLVQHYV 88

Src homology 2 (SH2) domain found in suppressor of cytokine signaling (SOCS) proteins; SH2 domain found in SOCS proteins. SOCS was first recognized as a group of cytokine-inducible SH2 (CIS) domain proteins comprising eight family members in human (CIS and SOCS1-SOCS7). In addition to the SH2 domain, SOCS proteins have a variable N-terminal domain and a conserved SOCS box in the C-terminal domain. SOCS proteins bind to a substrate via their SH2 domain. The prototypical members, CIS and SOCS1-SOCS3, have been shown to regulate growth hormone signaling in vitro and in a classic negative feedback response compete for binding at phosphotyrosine sites in JAK kinase and receptor pathways to displace effector proteins and target bound receptors for proteasomal degradation. Loss of SOCS activity results in excessive cytokine signaling associated with a variety of hematopoietic, autoimmune, and inflammatory diseases and certain cancers. Members (SOCS4-SOCS7) were identified by their conserved SOCS box, an adapter motif of 3 helices that associates substrate binding domains, such as the SOCS SH2 domain, ankryin, and WD40 with ubiquitin ligase components. These show limited cytokine induction. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  38 KALRELSQTGWYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLDSiicvkSKlK 117
Cdd:cd10382     2 RTSAMLDASGFYWGPLSVEEAHAKLKREPVGTFLIRDSRQKNCFFALSVKMASGPVSIRILFKAGKFSLDG-----SK-E 75

                          90
                  ....*....|....*..
gi 1039732729 118 QFDSVVHLIDYYVQMCK 134
Cdd:cd10382    76 SFDCLFKLLEHYVASPK 92

Src homology 2 (SH2) domain found in suppressor of cytokine signaling (SOCS) proteins; SH2 domain found in SOCS proteins. SOCS was first recognized as a group of cytokine-inducible SH2 (CIS) domain proteins comprising eight family members in human (CIS and SOCS1-SOCS7). In addition to the SH2 domain, SOCS proteins have a variable N-terminal domain and a conserved SOCS box in the C-terminal domain. SOCS proteins bind to a substrate via their SH2 domain. The prototypical members, CIS and SOCS1-SOCS3, have been shown to regulate growth hormone signaling in vitro and in a classic negative feedback response compete for binding at phosphotyrosine sites in JAK kinase and receptor pathways to displace effector proteins and target bound receptors for proteasomal degradation. Loss of SOCS activity results in excessive cytokine signaling associated with a variety of hematopoietic, autoimmune, and inflammatory diseases and certain cancers. Members (SOCS4-SOCS7) were identified by their conserved SOCS box, an adapter motif of 3 helices that associates substrate binding domains, such as the SOCS SH2 domain, ankryin, and WD40 with ubiquitin ligase components. These show limited cytokine induction. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  37 AKALRELSQTGWYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLdsiiCVKSKL 116
Cdd:cd10387     1 TEELKKLAKQGWYWGPITRWEAEGKLANVPDGSFLVRDSSDDRYLLSLSFRSHGKTLHTRIEHSNGRFSF----YEQPDV 76

                          90       100
                  ....*....|....*....|...
gi 1039732729 117 KQFDSVVHLIDYYVqmcKDKRTG 139
Cdd:cd10387    77 EGHTSIVDLIEHSI---RDSENG 96

SOCS (suppressors of cytokine signaling) box of SOCS2-like proteins. Together with CIS1, the CIS/SOCS family of proteins is characterized by the presence of a C-terminal SOCS box and a central SH2 domain. SOCS2 has recently been shown to regulate neuronal differentiation by controlling expression of a neurogenic transcription factor, Neurogenin-1. SOCS2 binds to GH receptors and inhibits the activation of STAT5b induced by GH. The general function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|
gi 1039732729 158 TSAPTLQHFCRLAINKCTGTIWGLPLPTRLKDYLEEYKFQ 197
Cdd:cd03736     1 TSTPSLQHLCRITINKCTRQIQELPLPTRLKDYLTEYTYH 40

Src homology 2 (SH2) domain found in suppressor of cytokine signaling (SOCS) proteins; SH2 domain found in SOCS proteins. SOCS was first recognized as a group of cytokine-inducible SH2 (CIS) domain proteins comprising eight family members in human (CIS and SOCS1-SOCS7). In addition to the SH2 domain, SOCS proteins have a variable N-terminal domain and a conserved SOCS box in the C-terminal domain. SOCS proteins bind to a substrate via their SH2 domain. The prototypical members, CIS and SOCS1-SOCS3, have been shown to regulate growth hormone signaling in vitro and in a classic negative feedback response compete for binding at phosphotyrosine sites in JAK kinase and receptor pathways to displace effector proteins and target bound receptors for proteasomal degradation. Loss of SOCS activity results in excessive cytokine signaling associated with a variety of hematopoietic, autoimmune, and inflammatory diseases and certain cancers. Members (SOCS4-SOCS7) were identified by their conserved SOCS box, an adapter motif of 3 helices that associates substrate binding domains, such as the SOCS SH2 domain, ankryin, and WD40 with ubiquitin ligase components. These show limited cytokine induction. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  39 ALRELSQTGWYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLDSiiCVKSKLKq 118
Cdd:cd10388     3 SLRELKDCGWYWGPMSWEDAEKVLSNKPDGSFLVRDSSDDRYIFSLSFRSQGSVHHTRIEQYQGTFSLGS--RNKFVDR- 79

                          90
                  ....*....|....*....
gi 1039732729 119 FDSVVHLIDYYVQMCKDKR 137
Cdd:cd10388    80 SQSLVEFIERAVEHSRSGR 98

SOCS (suppressors of cytokine signaling) box of SOCS-like proteins. The CIS/SOCS family of proteins is characterized by the presence of a C-terminal SOCS box and a central SH2 domain. These intracellular proteins regulate the responses of immune cells to cytokines. Identified as negative regulators of the cytokine-JAK-STAT pathway, they seem to play a role in many immunological and pathological processes. The function of the SOCS box is the recruitment of the ubiquitin-transferase system. Related SOCS boxes are also present in Rab40-like proteins and insect proteins of unknown function that also contain a NEUZ (domain in neuralized proteins) domain.

                          10        20        30
                  ....*....|....*....|....*....|....*....
gi 1039732729 158 TSAPTLQHFCRLAINKCTGT--IWGLPLPTRLKDYLEEY 194
Cdd:cd03717     1 TSVRSLQHLCRFVIRQCTRRdlIDQLPLPRRLKDYLKEY 39

SOCS (suppressors of cytokine signaling) box of CIS (cytokine-inducible SH2 protein) 1-like proteins. Together with the SOCS proteins, the CIS/SOCS family of proteins is characterized by the presence of a C-terminal SOCS box and a central SH2 domain. CIS1, like SOCS1 and SOCS3, is involved in the down-regulation of the JAK/STAT pathway. CIS1 binds to cytokine receptors at STAT5-docking sites, which prohibits recruitment of STAT5 to the receptor signaling complex and results in the down-regulation of activation by STAT5.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|
gi 1039732729 158 TSAPTLQHFCRLAINKCTGTIWGLPLPTRLKDYLEEYKFQ 197
Cdd:cd03734     1 SSARSLQHLCRLVINRLVTDVDCLPLPRRMADYLRQYPFQ 40

suppressors of cytokine signalling; suppressors of cytokine signalling

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|...
gi 1039732729  154 KPLYTSAPTLQHFCRLAINKCTGT--IWGLPLPTRLKDYLEEY 194
Cdd:smart00253   1 LPRPSNVPSLQHLCRFTIRRCTRTdqIKTLPLPPKLKDYLSYY 43

Src homology 2 (SH2) domain found in the Vav family; Vav proteins are involved in several processes that require cytoskeletal reorganization, such as the formation of the immunological synapse (IS), phagocytosis, platelet aggregation, spreading, and transformation. Vavs function as guanine nucleotide exchange factors (GEFs) for the Rho/Rac family of GTPases. Vav family members have several conserved motifs/domains including: a leucine-rich region, a leucine-zipper, a calponin homology (CH) domain, an acidic domain, a Dbl-homology (DH) domain, a pleckstrin homology (PH) domain, a cysteine-rich domain, 2 SH3 domains, a proline-rich region, and a SH2 domain. Vavs are the only known Rho GEFs that have both the DH/PH motifs and SH2/SH3 domains in the same protein. The leucine-rich helix-loop-helix (HLH) domain is thought to be involved in protein heterodimerization with other HLH proteins and it may function as a negative regulator by forming inactive heterodimers. The CH domain is usually involved in the association with filamentous actin, but in Vav it controls NFAT stimulation, Ca2+ mobilization, and its transforming activity. Acidic domains are involved in protein-protein interactions and contain regulatory tyrosines. The DH domain is a GDP-GTP exchange factor on Rho/Rac GTPases. The PH domain in involved in interactions with GTP-binding proteins, lipids and/or phosphorylated serine/threonine residues. The SH3 domain is involved in localization of proteins to specific sites within the cell interacting with protein with proline-rich sequences. The SH2 domain mediates a high affinity interaction with tyrosine phosphorylated proteins. There are three Vav mammalian family members: Vav1 which is expressed in the hematopoietic system, Vav2 and Vav3 are more ubiquitously expressed. The members here include insect and amphibian Vavs. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  42 ELSQTGWYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEY-QDGKFRLDSiicvkskLKQFD 120
Cdd:cd09940     1 DLSEFLWFVGEMERDTAENRLENRPDGTYLVRVRPQGETQYALSIKYNGDVKHMKIEQrSDGLYYLSE-------SRHFK 73

                  ....*....
gi 1039732729 121 SVVHLIDYY 129
Cdd:cd09940    74 SLVELVNYY 82

Src homology 2 (SH2) domain found in Nck; Nck proteins are adaptors that modulate actin cytoskeleton dynamics by linking proline-rich effector molecules to tyrosine kinases or phosphorylated signaling intermediates. There are two members known in this family: Nck1 (Nckalpha) and Nck2 (Nckbeta and Growth factor receptor-bound protein 4 (Grb4)). They are characterized by having 3 SH3 domains and a C-terminal SH2 domain. Nck1 and Nck2 have overlapping functions as determined by gene knockouts. Both bind receptor tyrosine kinases and other tyrosine-phosphorylated proteins through their SH2 domains. In addition they also bind distinct targets. Neuronal signaling proteins: EphrinB1, EphrinB2, and Disabled-1 (Dab-1) all bind to Nck-2 exclusively. And in the case of PDGFR, Tyr(P)751 binds to Nck1 while Tyr(P)1009 binds to Nck2. Nck1 and Nck2 have a role in the infection process of enteropathogenic Escherichia coli (EPEC). Their SH3 domains are involved in recruiting and activating the N-WASP/Arp2/3 complex inducing actin polymerization resulting in the production of pedestals, dynamic bacteria-presenting protrusions of the plasma membrane. A similar thing occurs in the vaccinia virus where motile plasma membrane projections are formed beneath the virus. Recently it has been shown that the SH2 domains of both Nck1 and Nck2 bind the G-protein coupled receptor kinase-interacting protein 1 (GIT1) in a phosphorylation-dependent manner. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  46 TGWYWGSMTVNEAKEKLKE-APEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFrldsiiCVKSklKQFDSVVH 124
Cdd:cd10409     1 KEWYYGNVTRHQAECALNErGVEGDFLIRDSESSPSDFSVSLKAVGKNKHFKVQLVDNVY------CIGQ--RRFNSMDE 72

                          90       100       110
                  ....*....|....*....|....*....|....*
gi 1039732729 125 LIDYYvqmckdkrtgPEAPRNGTVH---LYLTKPL 156
Cdd:cd10409    73 LVEHY----------KKAPIFTSEHgekLYLVKAL 97

C-terminal Src homology 2 (C-SH2) domain found in SH2 domain Phosphatases (SHP) proteins; The SH2 domain phosphatases (SHP-1, SHP-2/Syp, Drosophila corkscrew (csw), and Caenorhabditis elegans Protein Tyrosine Phosphatase (Ptp-2)) are cytoplasmic signaling enzymes. They are both targeted and regulated by interactions of their SH2 domains with phosphotyrosine docking sites. These proteins contain two SH2 domains (N-SH2, C-SH2) followed by a tyrosine phosphatase (PTP) domain, and a C-terminal extension. Shp1 and Shp2 have two tyrosyl phosphorylation sites in their C-tails, which are phosphorylated differentially by receptor and nonreceptor PTKs. Csw retains the proximal tyrosine and Ptp-2 lacks both sites. Shp-binding proteins include receptors, scaffolding adapters, and inhibitory receptors. Some of these bind both Shp1 and Shp2 while others bind only one. Most proteins that bind a Shp SH2 domain contain one or more immuno-receptor tyrosine-based inhibitory motifs (ITIMs): [SIVL]xpYxx[IVL]. Shp1 N-SH2 domain blocks the catalytic domain and keeps the enzyme in the inactive conformation, and is thus believed to regulate the phosphatase activity of SHP-1. Its C-SH2 domain is thought to be involved in searching for phosphotyrosine activators. The SHP2 N-SH2 domain is a conformational switch; it either binds and inhibits the phosphatase, or it binds phosphoproteins and activates the enzyme. The C-SH2 domain contributes binding energy and specificity, but it does not have a direct role in activation. Csw SH2 domain function is essential, but either SH2 domain can fulfill this requirement. The role of the csw SH2 domains during Sevenless receptor tyrosine kinase (SEV) signaling is to bind Daughter of Sevenless rather than activated SEV. Ptp-2 acts in oocytes downstream of sheath/oocyte gap junctions to promote major sperm protein (MSP)-induced MAP Kinase (MPK-1) phosphorylation. Ptp-2 functions in the oocyte cytoplasm, not at the cell surface to inhibit multiple RasGAPs, resulting in sustained Ras activation. It is thought that MSP triggers PTP-2/Ras activation and ROS production to stimulate MPK-1 activity essential for oocyte maturation and that secreted MSP domains and Cu/Zn superoxide dismutases function antagonistically to control ROS and MAPK signaling. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPE-GTFLIRDSSHS--DYLLTISVKTSAgPTNLRIEYQDGKFRLDSiicvkskLKQFDSVVH 124
Cdd:cd09931     2 WFHGHLSGKEAEKLLLEKGKpGSFLVRESQSKpgDFVLSVRTDDDK-VTHIMIRCQGGKYDVGG-------GEEFDSLTD 73

                          90       100       110
                  ....*....|....*....|....*....|....
gi 1039732729 125 LIDYYvqmckdkRTGPEAPRNGTVhLYLTKPLYT 158
Cdd:cd09931    74 LVEHY-------KKNPMVETSGTV-VHLKQPLNA 99

Src homology 2 domain found in SH2 domain-containing adapter protein E (SHE); SHE is expressed in heart, lung, brain, and skeletal muscle. SHE contains two pTry protein binding domains, protein interaction domain (PID) and a SH2 domain, followed by a glycine-proline rich region, all of which are N-terminal to the phosphotyrosine binding (PTB) domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRI-EYQDGKFRLDSIICVksklkqFDSVVHLI 126
Cdd:cd10391     3 WYHGSISRAEAESRLQPCKEASYLVRNSESGNSKYSIALKTSQGCVHIIVaQTKDNKYTLNQTSAV------FDSIPEVV 76

                          90       100       110
                  ....*....|....*....|....*....|
gi 1039732729 127 DYYvqmCKDKrtgpeAPRNGTVHLYLTKPL 156
Cdd:cd10391    77 HYY---SNEK-----LPFKGAEHMTLLHPV 98

C-terminal Src homology 2 (C-SH2) domain in Phospholipase C gamma; Phospholipase C gamma is a signaling molecule that is recruited to the C-terminal tail of the receptor upon autophosphorylation of a highly conserved tyrosine. PLCgamma is composed of a Pleckstrin homology (PH) domain followed by an elongation factor (EF) domain, 2 catalytic regions of PLC domains that flank 2 tandem SH2 domains (N-SH2, C-SH2), and ending with a SH3 domain and C2 domain. N-SH2 SH2 domain-mediated interactions represent a crucial step in transmembrane signaling by receptor tyrosine kinases. SH2 domains recognize phosphotyrosine (pY) in the context of particular sequence motifs in receptor phosphorylation sites. Both N-SH2 and C-SH2 have a very similar binding affinity to pY. But in growth factor stimulated cells these domains bind to different target proteins. N-SH2 binds to pY containing sites in the C-terminal tails of tyrosine kinases and other receptors. Recently it has been shown that this interaction is mediated by phosphorylation-independent interactions between a secondary binding site found exclusively on the N-SH2 domain and a region of the FGFR1 tyrosine kinase domain. This secondary site on the SH2 cooperates with the canonical pY site to regulate selectivity in mediating a specific cellular process. C-SH2 binds to an intramolecular site on PLCgamma itself which allows it to hydrolyze phosphatidylinositol-4,5-bisphosphate into diacylglycerol and inositol triphosphate. These then activate protein kinase C and release calcium. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPE-GTFLIRDSSHSDYLLTISVKTSAGPTNLRIEyQDGKfrldsIICVKSKlkQFDSVVHLI 126
Cdd:cd09932     6 WFHANLTREQAEEMLMRVPRdGAFLVRPSETDPNSFAISFRAEGKIKHCRIK-QEGR-----LFVIGTS--QFESLVELV 77

                  ...
gi 1039732729 127 DYY 129
Cdd:cd09932    78 SYY 80

Src homology 2 (SH2) domain found in Carboxyl-Terminal Src Kinase (Csk); Both the C-terminal Src kinase (CSK) and CSK-homologous kinase (CHK) are members of the CSK-family of protein tyrosine kinases. These proteins suppress activity of Src-family kinases (SFK) by selectively phosphorylating the conserved C-terminal tail regulatory tyrosine by a similar mechanism. CHK is also capable of inhibiting SFKs by a non-catalytic mechanism that involves binding of CHK to SFKs to form stable protein complexes. The unphosphorylated form of SFKs is inhibited by CSK and CHK by a two-step mechanism. The first step involves the formation of a complex of SFKs with CSK/CHK with the SFKs in the complex are inactive. The second step, involves the phosphorylation of the C-terminal tail tyrosine of SFKs, which then dissociates and adopt an inactive conformation. The structural basis of how the phosphorylated SFKs dissociate from CSK/CHK to adopt the inactive conformation is not known. The inactive conformation of SFKs is stabilized by two intramolecular inhibitory interactions: (a) the pYT:SH2 interaction in which the phosphorylated C-terminal tail tyrosine (YT) binds to the SH2 domain, and (b) the linker:SH3 interaction of which the SH2-kinase domain linker binds to the SH3 domain. SFKs are activated by multiple mechanisms including binding of the ligands to the SH2 and SH3 domains to displace the two inhibitory intramolecular interactions, autophosphorylation, and dephosphorylation of YT. By selective phosphorylation and the non-catalytic inhibitory mechanism CSK and CHK are able to inhibit the active forms of SFKs. CSK and CHK are regulated by phosphorylation and inter-domain interactions. They both contain SH3, SH2, and kinase domains separated by the SH3-SH2 connector and SH2 kinase linker, intervening segments separating the three domains. They lack a conserved tyrosine phosphorylation site in the kinase domain and the C-terminal tail regulatory tyrosine phosphorylation site. The CSK SH2 domain is crucial for stabilizing the kinase domain in the active conformation. A disulfide bond here regulates CSK kinase activity. The subcellular localization and activity of CSK are regulated by its SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPEGTFLIRDSSH--SDYllTISVKTSAGPTNLRIEYQDGKFRLDsiicvksKLKQFDSVVHL 125
Cdd:cd09937     5 WFHGKISREEAERLLQPPEDGLFLVRESTNypGDY--TLCVSFEGKVEHYRVIYRNGKLTID-------EEEYFENLIQL 75

                  ....
gi 1039732729 126 IDYY 129
Cdd:cd09937    76 VEHY 79

SOCS (suppressors of cytokine signaling) box of ASB (ankyrin repeat and SOCS box) and SSB (SPRY domain-containing SOCS box proteins) protein families. ASB family members have a C-terminal SOCS box and an N-terminal ankyrin-related sequence of a variable number of repeats. SSB proteins contain a central SPRY domain and a C-terminal SOCS. Recently, it has been shown that all four SSB proteins interact with the MET, the receptor protein-tyrosine kinase for hepatocyte growth factor (HGF), and that SSB-1, SSB-2, and SSB-4 interact with prostate apoptosis response protein-4. Both types of interactions are mediated through the SPRY domain.

                          10        20        30
                  ....*....|....*....|....*....|....*.
gi 1039732729 161 PTLQHFCRLAINKCTGT-----IWGLPLPTRLKDYL 191
Cdd:cd03716     4 RSLQHLCRLAIRRCLGRrrlelIKKLPLPPRLKDYL 39

Src homology 2 (SH2) domain found in SH2 adaptor protein C (SHC); SHC is involved in a wide variety of pathways including regulating proliferation, angiogenesis, invasion and metastasis, and bone metabolism. An adapter protein, SHC has been implicated in Ras activation following the stimulation of a number of different receptors, including growth factors [insulin, epidermal growth factor (EGF), nerve growth factor, and platelet derived growth factor (PDGF)], cytokines [interleukins 2, 3, and 5], erythropoietin, and granulocyte/macrophage colony-stimulating factor, and antigens [T-cell and B-cell receptors]. SHC has been shown to bind to tyrosine-phosphorylated receptors, and receptor stimulation leads to tyrosine phosphorylation of SHC. Upon phosphorylation, SHC interacts with another adapter protein, Grb2, which binds to the Ras GTP/GDP exchange factor mSOS which leads to Ras activation. SHC is composed of an N-terminal domain that interacts with proteins containing phosphorylated tyrosines, a (glycine/proline)-rich collagen-homology domain that contains the phosphorylated binding site, and a C-terminal SH2 domain. SH2 has been shown to interact with the tyrosine-phosphorylated receptors of EGF and PDGF and with the tyrosine-phosphorylated C chain of the T-cell receptor, providing one of the mechanisms of T-cell-mediated Ras activation. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  41 RELSQTGWYWGSMTVNEAKEKLKEapEGTFLIRDSSHS--DYLLTISvkTSAGPTNLRIeyqdgkfrLDSIICVKSKLKQ 118
Cdd:cd09925     2 EQLRGEPWYHGKMSRRDAESLLQT--DGDFLVRESTTTpgQYVLTGM--QNGQPKHLLL--------VDPEGVVRTKDRV 69

                          90
                  ....*....|...
gi 1039732729 119 FDSVVHLIDYYVQ 131
Cdd:cd09925    70 FESISHLINYHVT 82

Src homology 2 domain found in SH2 domain-containing adapter proteins B, D, E, and F (SHB, SHD, SHE, SHF); SHB, SHD, SHE, and SHF are SH2 domain-containing proteins that play various roles throughout the cell. SHB functions in generating signaling compounds in response to tyrosine kinase activation. SHB contains proline-rich motifs, a phosphotyrosine binding (PTB) domain, tyrosine phosphorylation sites, and a SH2 domain. SHB mediates certain aspects of platelet-derived growth factor (PDGF) receptor-, fibroblast growth factor (FGF) receptor-, neural growth factor (NGF) receptor TRKA-, T cell receptor-, interleukin-2 (IL-2) receptor- and focal adhesion kinase- (FAK) signaling. SRC-like FYN-Related Kinase FRK/RAK (also named BSK/IYK or GTK) and SHB regulate apoptosis, proliferation and differentiation. SHB promotes apoptosis and is also required for proper mitogenicity, spreading and tubular morphogenesis in endothelial cells. SHB also plays a role in preventing early cavitation of embryoid bodies and reduces differentiation to cells expressing albumin, amylase, insulin and glucagon. SHB is a multifunctional protein that has difference responses in different cells under various conditions. SHE is expressed in heart, lung, brain, and skeletal muscle, while expression of SHD is restricted to the brain. SHF is mainly expressed in skeletal muscle, brain, liver, prostate, testis, ovary, small intestine, and colon. SHD may be a physiological substrate of c-Abl and may function as an adapter protein in the central nervous system. It is also thought to be involved in apoptotic regulation. SHD contains five YXXP motifs, a substrate sequence preferred by Abl tyrosine kinases, in addition to a poly-proline rich region and a C-terminal SH2 domain. SHE contains two pTry protein binding domains, protein interaction domain (PID) and a SH2 domain, followed by a glycine-proline rich region, all of which are N-terminal to the phosphotyrosine binding (PTB) domain. SHF contains four putative tyrosine phosphorylation sites and an SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  47 GWYWGSMTVNEAKEKLKEAPEGTFLIRDS--SHSDYllTISVKTSAGPTNLRI-EYQDGKFRLDsiicvkSKLKQFDSVV 123
Cdd:cd09945     2 GWYHGAITRIEAESLLRPCKEGSYLVRNSesTKQDY--SLSLKSAKGFMHMRIqRNETGQYILG------QFSRPFETIP 73

                          90       100       110
                  ....*....|....*....|....*....|...
gi 1039732729 124 HLIDYYvqmckdkrTGPEAPRNGTVHLYLTKPL 156
Cdd:cd09945    74 EMIRHY--------CLNKLPVRGAEHMCLLEPV 98

Src homology 2 domain found in SH2 domain-containing adapter protein F (SHF); SHF is thought to play a role in PDGF-receptor signaling and regulation of apoptosis. SHF is mainly expressed in skeletal muscle, brain, liver, prostate, testis, ovary, small intestine, and colon. SHF contains four putative tyrosine phosphorylation sites and an SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRI-EYQDGKFRLDSIICVksklkqFDSVVHLI 126
Cdd:cd10392     3 WYHGAISRTDAENLLRLCKEASYLVRNSETSKNDFSLSLKSSQGFMHMKLsRTKEHKYVLGQNSPP------FSSVPEII 76

                          90       100       110
                  ....*....|....*....|....*....|
gi 1039732729 127 DYYVQMckdkrtgpEAPRNGTVHLYLTKPL 156
Cdd:cd10392    77 HHYASR--------KLPIKGAEHMSLLYPV 98

Src homology 2 (SH2) domain found in the Vav1 proteins; Proto-oncogene vav is a member of the Dbl family of guanine nucleotide exchange factors (GEF) for the Rho family of GTP binding proteins. All vavs are activated by tyrosine phosphorylation leading to their activation. There are three Vav mammalian family members: Vav1 which is expressed in the hematopoietic system, and Vav2 and Vav3 are more ubiquitously expressed. Vav1 plays a role in T-cell and B-cell development and activation. It has been identified as the specific binding partner of Nef proteins from HIV-1, resulting in morphological changes, cytoskeletal rearrangements, and the JNK/SAPK signaling cascade, leading to increased levels of viral transcription and replication. Vav1 has been shown to interact with Ku70, PLCG1, Lymphocyte cytosolic protein 2, Janus kinase 2, SIAH2, S100B, Abl gene, ARHGDIB, SHB, PIK3R1, PRKCQ, Grb2, MAPK1, Syk, Linker of activated T cells, Cbl gene and EZH2. Vav proteins are involved in several processes that require cytoskeletal reorganization, such as the formation of the immunological synapse (IS), phagocytosis, platelet aggregation, spreading, and transformation. Vavs function as guanine nucleotide exchange factors (GEFs) for the Rho/Rac family of GTPases. Vav family members have several conserved motifs/domains including: a leucine-rich region, a leucine-zipper, a calponin homology (CH) domain, an acidic domain, a Dbl-homology (DH) domain, a pleckstrin homology (PH) domain, a cysteine-rich domain, 2 SH3 domains, a proline-rich region, and a SH2 domain. Vavs are the only known Rho GEFs that have both the DH/PH motifs and SH2/SH3 domains in the same protein. The leucine-rich helix-loop-helix (HLH) domain is thought to be involved in protein heterodimerization with other HLH proteins and it may function as a negative regulator by forming inactive heterodimers. The CH domain is usually involved in the association with filamentous actin, but in Vav it controls NFAT stimulation, Ca2+ mobilization, and its transforming activity. Acidic domains are involved in protein-protein interactions and contain regulatory tyrosines. The DH domain is a GDP-GTP exchange factor on Rho/Rac GTPases. The PH domain in involved in interactions with GTP-binding proteins, lipids and/or phosphorylated serine/threonine residues. The SH3 domain is involved in localization of proteins to specific sites within the cell interacting with protein with proline-rich sequences. The SH2 domain mediates a high affinity interaction with tyrosine phosphorylated proteins. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  42 ELSQTGWYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLdsiicvkSKLKQFDS 121
Cdd:cd10405     1 DLSVHLWYAGPMERAGAESILANRSDGTYLVRQRVKDAAEFAISIKYNVEVKHIKIMTAEGLYRI-------TEKKAFRG 73

                          90
                  ....*....|
gi 1039732729 122 VVHLIDYYVQ 131
Cdd:cd10405    74 LTELVEFYQQ 83

Src homology 2 (SH2) domain found in the Vav2 proteins; Proto-oncogene vav is a member of the Dbl family of guanine nucleotide exchange factors (GEF) for the Rho family of GTP binding proteins. All vavs are activated by tyrosine phosphorylation leading to their activation. There are three Vav mammalian family members: Vav1 which is expressed in the hematopoietic system, and Vav2 and Vav3 are more ubiquitously expressed. Vav2 is a GEF for RhoA, RhoB and RhoG and may activate Rac1 and Cdc42. Vav2 has been shown to interact with CD19 and Grb2. Alternatively spliced transcript variants encoding different isoforms have been found for Vav2. Vav proteins are involved in several processes that require cytoskeletal reorganization, such as the formation of the immunological synapse (IS), phagocytosis, platelet aggregation, spreading, and transformation. Vavs function as guanine nucleotide exchange factors (GEFs) for the Rho/Rac family of GTPases. Vav family members have several conserved motifs/domains including: a leucine-rich region, a leucine-zipper, a calponin homology (CH) domain, an acidic domain, a Dbl-homology (DH) domain, a pleckstrin homology (PH) domain, a cysteine-rich domain, 2 SH3 domains, a proline-rich region, and a SH2 domain. Vavs are the only known Rho GEFs that have both the DH/PH motifs and SH2/SH3 domains in the same protein. The leucine-rich helix-loop-helix (HLH) domain is thought to be involved in protein heterodimerization with other HLH proteins and it may function as a negative regulator by forming inactive heterodimers. The CH domain is usually involved in the association with filamentous actin, but in Vav it controls NFAT stimulation, Ca2+ mobilization, and its transforming activity. Acidic domains are involved in protein-protein interactions and contain regulatory tyrosines. The DH domain is a GDP-GTP exchange factor on Rho/Rac GTPases. The PH domain in involved in interactions with GTP-binding proteins, lipids and/or phosphorylated serine/threonine residues. The SH3 domain is involved in localization of proteins to specific sites within the cell interacting with protein with proline-rich sequences. The SH2 domain mediates a high affinity interaction with tyrosine phosphorylated proteins. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLdsiicvkSKLKQFDSVVHLID 127
Cdd:cd10406     7 WFAGNMERQQTDNLLKSHASGTYLIRERPAEAERFAISIKFNDEVKHIKVVEKDNWIHI-------TEAKKFESLLELVE 79

                  ..
gi 1039732729 128 YY 129
Cdd:cd10406    80 YY 81

C-terminal Src homology 2 (SH2) domain found in SH2 domains, ANK, and kinase domain (shark) proteins; These non-receptor protein-tyrosine kinases contain two SH2 domains, five ankyrin (ANK)-like repeats, and a potential tyrosine phosphorylation site in its carboxyl-terminal tail which resembles the phosphorylation site in members of the src family. Like, mammalian non-receptor protein-tyrosine kinases, ZAP-70 and syk proteins, they do not have SH3 domains. However, the presence of ANK makes these unique among protein-tyrosine kinases. Both tyrosine kinases and ANK repeats have been shown to transduce developmental signals, and SH2 domains are known to participate intimately in tyrosine kinase signaling. These tyrosine kinases are believed to be involved in epithelial cell polarity. The members of this family include the shark (SH2 domains, ANK, and kinase domain) gene in Drosophila and yellow fever mosquitos, as well as the hydra protein HTK16. Drosophila Shark is proposed to transduce intracellularly the Crumbs, a protein necessary for proper organization of ectodermal epithelia, intercellular signal. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAP--EGTFLIRDSS--HSDYLLTISVKTSagPTNLRIEYQDGK-FRLDSiicvkskLKQFDSV 122
Cdd:cd10348     2 WLHGALDRNEAVEILKQKAdaDGSFLVRYSRrrPGGYVLTLVYENH--VYHFEIQNRDDKwFYIDD-------GPYFESL 72

                  ....*....
gi 1039732729 123 VHLIDYYVQ 131
Cdd:cd10348    73 EHLIEHYTQ 81

Src homology 2 domain found in Growth factor receptor-bound protein 2 (Grb2) and similar proteins; The adaptor proteins here include homologs Grb2 in humans, Sex muscle abnormal protein 5 (Sem-5) in Caenorhabditis elegans, and Downstream of receptor kinase (drk) in Drosophila melanogaster. They are composed of one SH2 and two SH3 domains. Grb2/Sem-5/drk regulates the Ras pathway by linking the tyrosine kinases to the Ras guanine nucleotide releasing protein Sos, which converts Ras to the active GTP-bound state. The SH2 domain of Grb2/Sem-5/drk binds class II phosphotyrosyl peptides while its SH3 domain binds to Sos and Sos-derived, proline-rich peptides. Besides it function in Ras signaling, Grb2 is also thought to play a role in apoptosis. Unlike most SH2 structures in which the peptide binds in an extended conformation (such that the +3 peptide residue occupies a hydrophobic pocket in the protein, conferring a modest degree of selectivity), Grb2 forms several hydrogen bonds via main chain atoms with the side chain of +2 Asn. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEA-PEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIeYQD--GKFRLDSiicVKsklkqFDSVVH 124
Cdd:cd09941     5 WFHGKISRAEAEEILMNQrPDGAFLIRESESSPGDFSLSVKFGNDVQHFKV-LRDgaGKYFLWV---VK-----FNSLNE 75

                  ....*
gi 1039732729 125 LIDYY 129
Cdd:cd09941    76 LVDYH 80

Src homology 2 domain found in SH2 domain-containing adapter protein B (SHB); SHB functions in generating signaling compounds in response to tyrosine kinase activation. SHB contains proline-rich motifs, a phosphotyrosine binding (PTB) domain, tyrosine phosphorylation sites, and a SH2 domain. SHB mediates certain aspects of platelet-derived growth factor (PDGF) receptor-, fibroblast growth factor (FGF) receptor-, neural growth factor (NGF) receptor TRKA-, T cell receptor-, interleukin-2 (IL-2) receptor- and focal adhesion kinase- (FAK) signaling. SRC-like FYN-Related Kinase FRK/RAK (also named BSK/IYK or GTK) and SHB regulate apoptosis, proliferation and differentiation. SHB promotes apoptosis and is also required for proper mitogenicity, spreading and tubular morphogenesis in endothelial cells. SHB also plays a role in preventing early cavitation of embryoid bodies and reduces differentiation to cells expressing albumin, amylase, insulin and glucagon. SHB is a multifunctional protein that has difference responses in different cells under various conditions. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKLKEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKFRLDsiicvkSKLKQFDSVVHLID 127
Cdd:cd10389     3 WYHGAISRGDAENLLRLCKECSYLVRNSQTSKHDYSLSLKSNQGFMHMKLAKTKEKYVLG------QNSPPFDSVPEVIH 76

                          90       100
                  ....*....|....*....|....*....
gi 1039732729 128 YYvqmckdkrTGPEAPRNGTVHLYLTKPL 156
Cdd:cd10389    77 YY--------TTRKLPIKGAEHLSLLYPV 97

Src homology 2 (SH2) domain found in tyrosine kinase sarcoma (Src); Src is a member of the Src non-receptor type tyrosine kinase family of proteins. Src is thought to play a role in the regulation of embryonic development and cell growth. Members here include v-Src and c-Src. v-Src lacks the C-terminal inhibitory phosphorylation site and is therefore constitutively active as opposed to normal cellular src (c-Src) which is only activated under certain circumstances where it is required (e.g. growth factor signaling). v-Src is an oncogene whereas c-Src is a proto-oncogene. c-Src consists of three domains, an N-terminal SH3 domain, a central SH2 domain and a tyrosine kinase domain. The SH2 and SH3 domains work together in the auto-inhibition of the kinase domain. The phosphorylation of an inhibitory tyrosine near the c-terminus of the protein produces a binding site for the SH2 domain which then facilitates binding of the SH3 domain to a polyproline site within the linker between the SH2 domain and the kinase domain. Binding of the SH3 domain inactivates the enzyme. This allows for multiple mechanisms for c-Src activation: dephosphorylation of the C-terminal tyrosine by a protein tyrosine phosphatase, binding of the SH2 domain by a competitive phospho-tyrosine residue, or competitive binding of a polyproline binding site to the SH3 domain. Unlike most other Src members Src lacks cysteine residues in the SH4 domain that undergo palmitylation. Serine and threonine phosphorylation sites have also been identified in the unique domains of Src and are believed to modulate protein-protein interactions or regulate catalytic activity. Alternatively spliced forms of Src, which contain 6- or 11-amino acid insertions in the SH3 domain, are expressed in CNS neurons. c-Src has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  48 WYWGSMTVNEAKEKL--KEAPEGTFLIRDSSHSDYLLTISVKTSAGPTNLRIEYQDGKfRLDSIICVKSKLKQFDSVVHL 125
Cdd:cd10365     5 WYFGKITRRESERLLlnAENPRGTFLVRESETTKGAYCLSVSDFDNAKGLNVKHYKIR-KLDSGGFYITSRTQFNSLQQL 83

                  ....*.
gi 1039732729 126 IDYYVQ 131
Cdd:cd10365    84 VAYYSK 89

SOCS (suppressors of cytokine signaling) box of ASB14-like proteins. ASB family members have a C-terminal SOCS box and an N-terminal ankyrin-related sequence. The general function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*..
gi 1039732729 158 TSAPTLQHFCRLAINKCTGTIW--------GLPLPTRLKDYL--EEY 194
Cdd:cd03730     1 TNPRSLKHLCRLKIRACMGRLRlrcpvfmsFLPLPNRLKAYIlyKEY 47

SOCS (suppressors of cytokine signaling) box of WSB/SWiP-like proteins. This subfamily contains WSB-1 (SOCS-box-containing WD-40 protein), part of an E3 ubiquitin ligase for the thyroid-hormone-activating type 2 iodothyronine deiodinase (D2), and SWiP-1 (SOCS box and WD-repeats in Protein), a WD40-containing protein that is expressed in embryonic structures of chickens and regulated by Sonic Hedgehog (Shh), as well as, their isoforms WSB-2 and SWiP-2. The general function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.

                          10        20        30
                  ....*....|....*....|....*....|....*
gi 1039732729 159 SAPTLQHFCRLAINKCTGT--IWGLPLPTRLKDYL 191
Cdd:cd03733     2 VVSSLQHLCRMALRRVMTTqqVLALPIPKKMKEFL 36

SOCS (suppressors of cytokine signaling) box of SOCS7-like proteins. Together with CIS1, the CIS/SOCS family of proteins is characterized by the presence of a C-terminal SOCS box and a central SH2 domain. SOCS7 is important in the functioning of neuronal cells. The general function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.

                          10        20        30
                  ....*....|....*....|....*....|....
gi 1039732729 162 TLQHFCRLAINKCT--GTIWGLPLPTRLKDYLEE 193
Cdd:cd03741     5 SLQHLCRFVIRKLVrrDHIPALPLPRRLIDYLRE 38

N-terminal Src homology 2 (N-SH2) domain in Phospholipase C gamma; Phospholipase C gamma is a signaling molecule that is recruited to the C-terminal tail of the receptor upon autophosphorylation of a highly conserved tyrosine. PLCgamma is composed of a Pleckstrin homology (PH) domain followed by an elongation factor (EF) domain, 2 catalytic regions of PLC domains that flank 2 tandem SH2 domains (N-SH2, C-SH2), and ending with a SH3 domain and C2 domain. N-SH2 SH2 domain-mediated interactions represent a crucial step in transmembrane signaling by receptor tyrosine kinases. SH2 domains recognize phosphotyrosine (pY) in the context of particular sequence motifs in receptor phosphorylation sites. Both N-SH2 and C-SH2 have a very similar binding affinity to pY. But in growth factor stimulated cells these domains bind to different target proteins. N-SH2 binds to pY containing sites in the C-terminal tails of tyrosine kinases and other receptors. Recently it has been shown that this interaction is mediated by phosphorylation-independent interactions between a secondary binding site found exclusively on the N-SH2 domain and a region of the FGFR1 tyrosine kinase domain. This secondary site on the SH2 cooperates with the canonical pY site to regulate selectivity in mediating a specific cellular process. C-SH2 binds to an intramolecular site on PLCgamma itself which allows it to hydrolyze phosphatidylinositol-4,5-bisphosphate into diacylglycerol and inositol triphosphate. These then activate protein kinase C and release calcium. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039732729  57 EAKEKLKE---APEGTFLIRDSSH--SDYllTISVKTSAGPTNLRIEYQDG----KFRLDSIicvksklKQFDSVVHLID 127
Cdd:cd10341    17 EAEKLLLEyceGGDGTFLVRESETfvGDY--TLSFWRNGKVQHCRIRSRQEngekKYYLTDN-------LVFDSLYELID 87

                  ....*
gi 1039732729 128 YYVQM 132
Cdd:cd10341    88 YYRQN 92

C-terminal Src homology 2 (SH2) domain found in Ras GTPase-activating protein 1 (GAP); RasGAP is part of the GAP1 family of GTPase-activating proteins. The protein is located in the cytoplasm and stimulates the GTPase activity of normal RAS p21, but not its oncogenic counterpart. Acting as a suppressor of RAS function, the protein enhances the weak intrinsic GTPase activity of RAS proteins resulting in RAS inactivation, thereby allowing control of cellular proliferation and differentiation. Mutations leading to changes in the binding sites of either protein are associated with basal cell carcinomas. Alternative splicing results in two isoforms. The shorter isoform which lacks the N-terminal hydrophobic region, has the same activity, and is expressed in placental tissues. In general longer isoform contains 2 SH2 domains, a SH3 domain, a pleckstrin homology (PH) domain, and a calcium-dependent phospholipid-binding C2 domain. The C-terminus contains the catalytic domain of RasGap which catalyzes the activation of Ras by hydrolyzing GTP-bound active Ras into an inactive GDP-bound form of Ras. This model contains the C-terminal SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....
gi 1039732729  48 WYWGSMTVNEAKEKL-KEAPEGTFLIRDSSHS--DYllTISVKTSAGPTNLRIE 98
Cdd:cd10354     2 WFHGKISREEAYNMLvKVGGPGSFLVRESDNTpgDY--SLSFRVNEGIKHFKII 53

Src homology 2 (SH2) domain found in the Src family of non-receptor tyrosine kinases; The Src family kinases are nonreceptor tyrosine kinases that have been implicated in pathways regulating proliferation, angiogenesis, invasion and metastasis, and bone metabolism. It is thought that transforming ability of Src is linked to its ability to activate key signaling molecules in these pathways, rather than through direct activity. As such blocking Src activation has been a target for drug companies. Src family members can be divided into 3 groups based on their expression pattern: 1) Src, Fyn, and Yes; 2) Blk, Fgr, Hck, Lck, and Lyn; and 3) Frk-related kinases Frk/Rak and Iyk/Bsk Of these, cellular c-Src is the best studied and most frequently implicated in oncogenesis. The c-Src contains five distinct regions: a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Src exists in both active and inactive conformations. Negative regulation occurs through phosphorylation of Tyr, resulting in an intramolecular association between phosphorylated Tyr and the SH2 domain of SRC, which locks the protein in a closed conformation. Further stabilization of the inactive state occurs through interactions between the SH3 domain and a proline-rich stretch of residues within the kinase domain. Conversely, dephosphorylation of Tyr allows SRC to assume an open conformation. Full activity requires additional autophosphorylation of a Tyr residue within the catalytic domain. Loss of the negative-regulatory C-terminal segment has been shown to result in increased activity and transforming potential. Phosphorylation of the C-terminal Tyr residue by C-terminal Src kinase (Csk) and Csk homology kinase results in increased intramolecular interactions and consequent Src inactivation. Specific phosphatases, protein tyrosine phosphatase a (PTPa) and the SH-containing phosphatases SHP1/SHP2, have also been shown to take a part in Src activation. Src is also activated by direct binding of focal adhesion kinase (Fak) and Crk-associated substrate (Cas) to the SH2 domain. SRC activity can also be regulated by numerous receptor tyrosine kinases (RTKs), such as Her2, epidermal growth factor receptor (EGFR), fibroblast growth factor receptor, platelet-derived growth factor receptor (PDGFR), and vascular endothelial growth factor receptor (VEGFR). In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|.
gi 1039732729  48 WYWGSMTVNEAKEKLKEA--PEGTFLIRDSSHS--DYLLTI 84
Cdd:cd09933     5 WFFGKIKRKDAEKLLLAPgnPRGTFLIRESETTpgAYSLSV 45

SOCS (suppressors of cytokine signaling) box of SOCS6-like proteins. Together with CIS1, the CIS/SOCS family of proteins is characterized by the presence of a C-terminal SOCS box and a central SH2 domain. The general function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.

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                  ....*....|....*....|....*....|....*..
gi 1039732729 162 TLQHFCRLAINKCT--GTIWGLPLPTRLKDYLEEYKF 196
Cdd:cd03740     5 SLQYLCRFVIRQYTriDLIQKLPLPNKMKGYLLEKHY 41