A new member of the ras superfamily, the rac1 homologue from Caenorhabditis elegans. Cloning and sequence analysis of cDNA, pattern of developmental expression, and biochemical characterization of the protein.

A new member of the ras superfamily, designated CErac1 has been identified. The CErac1 cDNA clone was isolated from a Caenorhabditis elegans mixed stage library and encodes a protein of 191 amino acids with 82 and 79% identity to human rac1 and rac2 proteins, respectively. The CErac1 cDNA maps to a position on C. elegans chromosome IV in close proximity to cha-1, a choline acetyltransferase gene. The CErac1 cDNA hybridizes to two mRNAs (1.7 and 0.9 kilobases). Their expression is developmentally regulated, that of the more abundant 1.7 kilobases being highest at the embryonic stage and decreasing dramatically during development with 10% of the embryonic level in adult nematodes. The glutathione-S-transferase/CErac1 fusion protein expressed in Escherichia coli binds GTP and exhibits intrinsic GTPase activity. The GTPase activity of the CErac1 protein is stimulated by human n-chimaerin, a GTPase-activating protein for p21 rac1. These data suggest a role of CErac1 in C. elegans early development. The conserved biochemical properties indicate that further characterization of CErac1 by genetic analysis will be helpful in elucidating not only its role in the signal transduction, but also the biological function of its mammalian homologues.