Identification and partial purification of GTPase‐activating proteins from yeast and mammalian cells that preferentially act on Ypt1/Rab1 proteins

Abstract

Two GTPase‐activating proteins of apparent molecular mass of 100 kDa and 30 kDa have been partially purified from porcine liver cytosol usinig mammalian Ypt1/Rab1 protein as substrate. Both proteins act most efficiently on Ypt1/Rab1 p, but are inactive with H‐Ras p21. From the budding yeast Saccharomyces cerevisiae, a cytosolic 40 kDa yptGAP was partially purified. It accelerates the intrinsic GTPase activity of wild‐type Yptlp but not of H‐Ras p21 or a mutant ypt1p with an animo acid substitution of the effector domain which renders the protein functionally inactive in yeast cells.