Src homology 3 domain of the Tight junction protein, Zonula occludens protein 2
ZO-2 is a scaffolding protein that associates with other ZO proteins and other proteins of the tight junction, zonula adherens, and gap junctions. ZO proteins play roles in regulating cytoskeletal dynamics at these cell junctions. ZO-2 plays an essential role in embryonic development. It is critical for the blood-testis barrier integrity and male fertility. It also regulates the expression of cyclin D1 and cell proliferation. It is considered a member of the MAGUK (membrane-associated guanylate kinase) protein family, which is characterized by the presence of a core of three domains: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. The C-terminal region of ZO-2 contains an actin-binding region and a domain of unknown function designated beta. The SH3 domain of the related protein ZO-1 has been shown to bind ZONAB, ZAK, afadin, and Galpha12. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.
Jiyao W et al.(2023). "The conserved domain database in 2023.",