title: Ras GTPase activating (RasGAP) activity of the dual specificity GAP protein Rasal requires colocalization and C2 domain binding to lipid membranes.
abstract: Rasal, belonging to the GAP1 subfamily of Ras GTPase-activating proteins (RasGAPs) with dual RasGAP/RapGAP specificity, is epigenetically silenced in several tumor types. Surprisingly, the isolated protein has GAP activity on Rap but not on Ras. Its membrane recruitment is regulated by interaction with calcium and lipids, which simultaneously induces its RasGAP activity through a yet unknown mechanism. Here we show that the interaction of Rasal with membranes induces Rasal RasGAP activity by spatial and conformational regulation, although it does not have any effect on its RapGAP activity. Not only is colocalization of Rasal and Ras in the membrane essential for RasGAP activation, but direct and Ca-dependent interaction between the tandem C2 domains of Rasal and lipids of the membrane is also required. Whereas the C2A domain binds specifically phosphatidylserine, the C2B domain interacts with several phosphoinositol lipids. Finally we show, that similar to the C2 domains of synaptotagmins, the Rasal tandem C2 domains are able to sense and induce membrane curvature by the insertion of hydrophobic loops into the membrane.
authors.affiliation: Department of Structural Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany.
authors.forename: Begoña
authors.initials: B
authors.lastname: Sot
authors.forename: Elmar
authors.initials: E
authors.lastname: Behrmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Raunser
authors.forename: Alfred
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D000595:Amino Acid Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000502:physiology; D004926:Escherichia coli; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D020729:p120 GTPase Activating Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D018129:Phosphatidylinositol Phosphates; D010718:Phosphatidylserines; C557248:RASA1 protein, human; D020729:p120 GTPase Activating Protein