title: GTPase activity of Di-Ras proteins is stimulated by Rap1GAP proteins.
abstract: The Ras family is the largest and most diverse sub-group of Ras-like G proteins. This complexity is further increased by the high number of regulatory Guanine nucleotide Exchange Factors (GEFs) and GTPase Activating Proteins (GAPs) that target specific members of this subfamily. Di-Ras1 and Di-Ras2 are little characterized members of the Ras-like sub-group with still unidentified regulatory and effector proteins. Here we determined the nucleotide binding properties of Di-Ras1/Di-Ras2. The above nanomolar affinity and the inability to react with members of the Cdc25 RasGEF family might suggest that activation does not require a GEF. We identified Rap1GAP1 and Rap1GAP2 as specific GTPase activating proteins of the Di-Ras family. Dual-specificity GAPs of the GAP1(m) family could not activate Di-Ras proteins, despite the presence of the required catalytic residue. Although Di-Ras proteins share GAPs with Rap G proteins, no common effectors could be identified in vitro.
authors.affiliation: Max-Planck-Institut für Molekulare Physiologie; Abteilung Strukturelle Biologie; Dortmund, Germany.
authors.forename: Raphael
authors.initials: R
authors.lastname: Gasper
authors.forename: Begoña
authors.initials: B
authors.lastname: Sot
authors.forename: Alfred
authors.initials: A
authors.lastname: Wittinghofer