Crystal structure of a small G protein in complex with the GTPase-activating protein rhoGAP

• Published in: Nature (London) Vol. 388; no. 6643; pp. 693 - 697
• Main Authors: Gamblin, Steven J, Rittinger, Katrin, Walker, Philip A, Eccleston, John F, Nurmahomed, Kurshid, Owen, Darerca, Laue, Ernest, Smerdon, Stephen J
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 14.08.1997; Nature Publishing Group
• Subjects: Analytical, structural and metabolic biochemistry; Arginine - chemistry; Binding and carrier proteins; Biological and medical sciences; cdc42 GTP-Binding Protein; Cell Cycle Proteins - chemistry; Chemical reactions; Crystalline structure; Crystallography, X-Ray; Enzyme Activation; Fundamental and applied biological sciences. Psychology; GTP Phosphohydrolases - metabolism; GTP-Binding Proteins - chemistry; GTPase-Activating Proteins; Guanosine Triphosphate - analogs & derivatives; Guanosine Triphosphate - chemistry; Hydrolysis; Models, Molecular; Molecular biology; Molecular biophysics; Protein Conformation; Proteins; Structure in molecular biology; Studies; Binding protein; GTP; Molecular structure; Molecular complex; G protein; Crystalline structure; GTPase activating protein
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/41805

Small G proteins transduce signals from plasma-membrane receptors to control a wide range of cellular functions,. These proteins are clustered into distinct families but all act as molecular switches, active in their GTP-bound form but inactive when GDP-bound. The Rho family of G proteins, which includes Cdc42Hs, activate effectors involved in the regulation of cytoskeleton formation, cell proliferation and the JNK signalling pathway. G proteins generally have a low intrinsic GTPase hydrolytic activity but there are family-specific groups of GTPase-activating proteins (GAPs) that enhance the rate of GTP hydrolysis by up to 105times,. We report here the crystal structure of Cdc42Hs, with the non-hydrolysable GTP analogue GMPPNP, in complex with the GAP domain of p50rhoGAP at 2.7 å resolution. In the complex Cdc42Hs interacts, mainly through its switch I and II regions, with a shallow pocket on rhoGAP which is lined with conserved residues. Arg 85 of rhoGAP interacts with the P-loop of Cdc42Hs, but from biochemical data and by analogy with the G-protein subunit Giα1 (ref. 12), we propose that it adopts a different conformation during the catalytic cycle which enables it to stabilize the transition state of the GTP-hydrolysis reaction.