Primary Citation of Related Structures:   1K5D, 1K5G
PubMed Abstract: 
GTPase-activating proteins (GAPs) increase the rate of GTP hydrolysis on guanine nucleotide-binding proteins by many orders of magnitude. Studies with Ras and Rho have elucidated the mechanism of GAP action by showing that their catalytic machinery is both stabilized by GAP binding and complemented by the insertion of a so-called 'arginine finger' into the phosphate-binding pocket ...
GTPase-activating proteins (GAPs) increase the rate of GTP hydrolysis on guanine nucleotide-binding proteins by many orders of magnitude. Studies with Ras and Rho have elucidated the mechanism of GAP action by showing that their catalytic machinery is both stabilized by GAP binding and complemented by the insertion of a so-called 'arginine finger' into the phosphate-binding pocket. This has been proposed as a universal mechanism for GAP-mediated GTP hydrolysis. Ran is a nuclear Ras-related protein that regulates both transport between the nucleus and cytoplasm during interphase, and formation of the mitotic spindle and/or nuclear envelope in dividing cells. Ran-GTP is hydrolysed by the combined action of Ran-binding proteins (RanBPs) and RanGAP. Here we present the three-dimensional structure of a Ran-RanBP1-RanGAP ternary complex in the ground state and in a transition-state mimic. The structure and biochemical experiments show that RanGAP does not act through an arginine finger, that the basic machinery for fast GTP hydrolysis is provided exclusively by Ran and that correct positioning of the catalytic glutamine is essential for catalysis.
Related Citations: 
THE RAS-RASGAP COMPLEX: STRUCTURAL BASIS FOR GTPASE ACTIVATION AND ITS LOSS IN ONCOGENIC RAS MUTANTS Scheffzek, K., Ahmadian, M.R., Kabsch, W., Wiesmueller, L., Lautwein, A., Schmitz, F., Wittinghofer, A. (1997) Science 277: 333
STRUCTURE OF A RAN-BINDING DOMAIN COMPLEXED WITH RAN BOUND TO A GTP ANALOGUE: IMPLICATIONS FOR NUCLEAR TRANSPORT Vetter, I.R., Nowak, C., Nishimoto, T., Kuhlmann, J., Wittinghofer, A. (1999) Nature 398: 39
THE CRYSTAL STRUCTURE OF RNA1P: A NEW FOLD FOR A GTPASE-ACTIVATING PROTEIN Hillig, R.C., Renault, L., Vetter, I.R., Drell, T., Wittinghofer, A., Becker, J. (1999) Mol Cell 3: 781
RNA1 ENCODES A GTPASE-ACTIVATING PROTEIN SPECIFIC FOR GSP1P, THE RAN/TC4 HOMOLOGUE OF SACCHAROMYCES CEREVISIAE Becker, J., Melchior, F., Gerke, V., Bischoff, F.R., Ponstingl, H., Wittinghofer, A. (1995) J Biol Chem 270: 11860
THE ACIDIC C-TERMINAL DOMAIN OF RNA1P IS REQUIRED FOR THE BINDING OF RAN.GTP AND FOR RANGAP ACTIVITY Haberland, J., Becker, J., Gerke, V. (1997) J Biol Chem 272: 24717
Organizational Affiliation: 
Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Dortmund, Germany.