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Src Homology 3 domain of Class B Dedicator of Cytokinesis 3 Dock3, also called modifier of cell adhesion (MOCA), and presenilin binding protein (PBP), is a class B DOCK and is an atypical guanine nucleotide exchange factor (GEF) that lacks the conventional Dbl homology (DH) domain. It regulates N-cadherin dependent cell-cell adhesion, cell polarity, and neuronal morphology. It promotes axonal growth by stimulating actin polymerization and microtubule assembly. All DOCKs contain two homology domains: the DHR-1 (Dock homology region-1), also called CZH1 (CED-5, Dock180, and MBC-zizimin homology 1), and DHR-2 (also called CZH2 or Docker). The DHR-1 domain binds phosphatidylinositol-3,4,5-triphosphate while DHR-2 contains the catalytic activity for Rac and/or Cdc42. Class B DOCKs also contain an SH3 domain at the N-terminal region and a PxxP motif at the C-terminus; Dock3 is a specific GEFs for Rac. The SH3 domain of Dock3 binds to DHR-2 in an autoinhibitory manner; binding of the scaffold protein Elmo to the SH3 domain of Dock3 exposes the DHR-2 domain and promotes GEF activity. 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.",