Ras GTPase-activating-like protein IQGAP1; p195; IQ motif-containing GTPase-activating protein 1IQGAP1; RasGAP-like with IQ motifs; homolog of S. pombe SAR1 (IQGAP1, KIAA0051)

^[1]^[2]^[3]

Function

binds to activated CDC42
does not stimulate CDC42 GTPase activity
associates with calmodulin
could serve as an assembly scaffold for the organization of a multimolecular complex that would interface incoming signals to the reorganization of the actin cytoskeleton at the plasma membrane
may promote neurite outgrowth
phosphorylation of Ser-1443 by PKC/PRKCE prevents interaction between regions C1 & C2, allowing binding of nucleotide-free CDC42
Ser- 1443 phosphorylation enhances the ability to promote neurite outgrowth
interacts with CDC42 in GTP-bound & in nucleotide-free state
interacts with RAC1
does not interact with RHOA
interacts with TSG101
interacts with PAK6

regions C1 & C2 can either interact with nucleotide-free CDC42, or interact together, depending on the phosphorylation state of Ser-1443
when Ser-1443 is not phosphorylated, C1 & C2 regions interact, which prevents binding of nucleotide-free CDC42 & promotes binding of GTP-bound CDC42
phosphorylation of Ser-1443 prevents interaction between C1 & C2 regions, which opens the structure of the C-terminus & allows binding & sequestration of nucleotide-free CDC42 on both regions C1 & C2
contains 1 CH (calponin-homology) domain
contains 4 IQ domains
contains 1 Ras-GAP domain
contains 1 WW domain

↑ UniProt http://www.uniprot.org/uniprot/P46940.html
↑ Boguski MS & McCormick F Proteins regulating Ras and its relative. Nature 366:643 1993 PMID: https://www.ncbi.nlm.nih.gov/pubmed/8259209
↑ Pawson T. Protein modules and signalling networks. Nature. 1995 Feb 16;373(6515):573-80. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/7531822