Monomeric GTPases of the Ras superfamily have a very slow intrinsic GTPase activity which is accelerated by specific GTPase-activating proteins. In contrast to Ras- and Rho-specific GTPase-activating proteins (GAPs) that have been studied in great detail, little is known about the functioning of GAPs specific for Ypt/Rab transport GTPases. We have identified two novel Ypt/Rab-GAPs because of their sequence relatedness to the three known GAPs Gyp1p, Gyp6p, and Gyp7p. Mdr1/Gyp2p is an efficient GAP for Ypt6p and Sec4p, whereas Msb3/Gyp3p is a potent GAP for Sec4p, Ypt6p, Ypt51p, Ypt31/Ypt32p, and Ypt1p. Although the affinity of Msb3/Gyp3p for its preferred substrate Sec4p is low (K(m) = 154 microM), it accelerates the intrinsic GTPase activity of Sec4p 5 x 10(5)-fold. Msb3/Gyp3p appears to be functionally linked to Cdc42p-regulated pathway(s). The results demonstrate that in yeast there is a large family of Ypt/Rab-GAPs, members of which discriminate poorly between GTPases involved in regulating different steps of exo- and endocytic transport routes.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|