(= guanine nucleotide exchange factors.) Family of proteins that facilitate the exchange of bound GDP for GTP on small G-proteins such as ras and rho and thus activate them. Act in the opposite way to GAPs (which promote the hydrolysis of bound GTP, thereby switching the G protein to the inactive form). Family includes cytohesin, ARNO, Gea-1 and 2, kalirin and yeast Sec7.
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