title: Enzymatic GTP hydrolysis: insights from an ab initio molecular dynamics study.
abstract: Ab initio methods were used to shed light on fundamental aspects of the enzymatic mechanism of guanosine triphosphate hydrolysis in the Cdc42/Cdc42GAP complex. The calculations focused on the nucleophilic addition of the catalytic water molecule to the gamma-phosphate phosphorus atom. A large model system was required to correctly reproduce the electrostatic properties on the active site. The model turned out to reproduce most of the electrostatic field of the biological complex at the reactants. Our calculations established the H-bond pattern of the catalytic water (WAT), which turned out to interact with Q61 and T35, in the most stable conformation. This ruled out the possibility that the catalytic water transferred its proton directly to the gamma-phosphate. Furthermore, the calculations suggested that the electronic structure of WAT was very different from that in the bulk. Finally, this study showed that during the reaction, WAT transferred a proton to Gln61, consistent with the available X-ray data on a transition-state analogue/enzyme complex(19) and with the decrease of activity in the Q61E mutant.
authors.affiliation: Scuola Internazionale Superiore di Studi Avanzati, Istituto Nazionale di Fisica della Materia, Via Beirut 2-4, I-34014 Trieste, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cavalli
authors.forename: Paolo
authors.initials: P
authors.lastname: Carloni
mesh_terms: D001665:Binding Sites; D003198:Computer Simulation; D006160:Guanosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D008958:Models, Molecular; D011789:Quantum Theory; D055672:Static Electricity; D014867:Water / Q000737:chemistry* / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry* / Q000378:metabolism
chemical_list: D014867:Water; D006160:Guanosine Triphosphate; D020764:cdc42 GTP-Binding Protein