SH3 domain-binding protein 1 (Sh3bp1)

GTPase activating protein (GAP) which specifically converts GTP-bound Rho-type GTPases including RAC1 and CDC42 in their inactive GDP-bound form (PubMed:7621827). By specifically inactivating RAC1 in the leading edge of migrating cells, it modulates the spatiotemporal organization of cell protrusions that's essential for proper cell migration.

Additionally negatively modulates CDC42 in the process of actin remodeling and the creation of epithelial cell junctions. Through its GAP activity toward RAC1 and/or CDC42 plays a particular role in phagocytosis of large particles.