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Publication Abstract from PubMed

GTP hydrolysis by small GTP binding proteins of the Ras superfamily is a universal reaction that controls multiple cellular regulations. Its enzymic mechanism has been the subject of long-standing debates as to the existence/identity of the general base and the electronic nature of its transition state. Here we report the high-resolution crystal structure of a small GTP binding protein, Rab11, solved in complex with GDP and Pi. Unexpectedly, a Pi oxygen and the GDP-cleaved oxygen are located less than 2.5 A apart, suggesting that they share a proton, likely in the form of a low-barrier hydrogen bond. This implies that the gamma-phosphate of GTP was protonated; hence, that GTP acts as a general base. Furthermore, this interaction should establish at, and stabilize, the transition state. Altogether, we propose a revised model for the GTPase reaction that should reconcile earlier models into a unique substrate-assisted mechanism.

Crystallographic evidence for substrate-assisted GTP hydrolysis by a small GTP binding protein.,Pasqualato S, Cherfils J Structure. 2005 Apr;13(4):533-40. PMID:15837192^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.