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Ras-associating (RA) domain found in Rap1-GTP-interacting adapter molecule (RIAM) RIAM, also termed amyloid beta A4 precursor protein-binding family B member 1-interacting protein, or APBB1-interacting protein 1, or proline-rich EVH1 ligand 1 (PREL-1), or proline-rich protein 73, or retinoic acid-responsive proline-rich protein 1 (RARP-1), is a member of MRL (Mig10/RIAM/Lpd) family proteins that regulates cell migration and promote lamellipodia protrusion in fibroblast by interacting with Ena/VASP proteins. RIAM regulates cell migration and mediates Rap1-induced cell adhesion. MRL proteins share a common structural architecture, including a central structural unit consisting of an RA domain and a pleckstrin homology (PH) domain, an upstream coiled-coil region, and a number of polyproline motifs. RA domain-containing proteins function by interacting with Ras proteins directly or indirectly and are involved in several different functions ranging from tumor suppression to being oncoproteins. RA domain has the beta-grasp ubiquitin-like fold with low sequence similarity to ubiquitin (Ub). Ub is a protein modifier in eukaryotes that is involved in various cellular processes including transcriptional regulation, cell cycle control, and DNA repair in eukaryotes. RIAM also contains a helical region at the amino terminus for talin binding. RA and PH form a tandem domain pair (RA-PH), and serve tightly coordinated functions in both Ras GTPase signaling via the RA domain and membrane translocalization via the PH domain.
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