Ras-GTPase Activating Domain of IQ motif containing GTPase activating proteins
This family represents IQ motif containing GTPase activating protein (IQGAP) which associated with the Ras GTP-binding protein. A primary function of IQGAP proteins is to modulate cytoskeletal architecture. There are three known IQGAP family members: IQGAP1, IQGAP2 and IQGAP3. Human IQGAP1 and IQGAP2 share 62% identity. IQGAPs are multi-domain molecules having a calponin-homology (CH) domain which binds F-actin, IQGAP-specific repeats, a single WW domain, four IQ motifs that mediate interactions with calmodulin, and a RasGAP related domain that binds active Rho family GTPases. IQGAP is an essential regulator of cytoskeletal function. IQGAP1 negatively regulates Ras family GTPases by stimulating their intrinsic GTPase activity, the protein actually lacks GAP activity. Both IQGAP1 and IQGAP2 specifically bind to Cdc42 and Rac1, but not to RhoA. Despite of their similarities to part of the sequence of RasGAP, neither IQGAP1 nor IQGAP2 interacts with Ras. IQGAP3, only present in mammals, regulates the organization of the cytoskeleton under the regulation of Rac1 and Cdc42 in neuronal cells. The depletion of IQGAP3 is shown to impair neurite or axon outgrowth in neuronal cells with disorganized cytoskeleton.
Jiyao W et al.(2023). "The conserved domain database in 2023.",