ADP Ribosylation Factor Guanine Nucleotide Exchange Factor 1 (ARFGEF1)

ARFGEF1 is involved in the activation of ARFs by accelerating replacement of bound GDP with GTP. It contains a Sec7 domain, which may be responsible for the guanine-nucleotide exchange activity and also the brefeldin A inhibition.

BIG1 and MYO9B bound with a 1-to-1 stoichiometry, and mutation analysis showed that BIG1 bound specifically to the zinc finger/GAP domain of MYO9B. Binding of BIG1 to MYO9B interfered with binding of RhoA to MYO9B and inhibited the Rho-GAP activity of MYO9B in a dose-dependent manner. Likewise, RhoA inhibited binding of BIG1 to MYO9B. Binding of MYO9B to BIG1 did not alter the ARF-GEF activity of BIG1.The full-length BIG1 cDNA encodes a protein of 1,849 amino acids containing a Sec7 domain characteristic of ARF guanine nucleotide-exchange proteins.