The yeast Rgd1p is a GTPase activating protein of the Rho3 and Rho4 proteins

The RGD1 gene, identified during sequencing of the Saccharomyces cerevisiae genome, encodes a protein with a Rho-GTPase activating protein (GAP) domain at the carboxyterminal end. The Rgd1 protein showed two-hybrid interactions with the activated forms of Rho2p, Rho3p and Rho4p, Using in vitro assays, we demonstrated that Rgd1p stimulated the GTPase activity of both Rho3p and Rho4p; no stimulation was observed on Rho2p, In addition, the rho3 Delta rgdI Delta double mutant exhibited a dramatic growth defect compared to the single mutants, suggesting that Rgd1p has a GAP activity in vivo. The present study allowed the identification of the first GAP of Rho3p and Rho4p. (C) 1999 Federation of European Biochemical Societies.