Ras-catalyzed hydrolysis of GTP: a new perspective from model studies.

摘要: Despite the biological and medical importance of signal transduction via Ras proteins despite considerable kinetic structural studies wild-type mutant proteins, mechanism Ras-catalyzed GTP hydrolysis remains controversial. We take a different approach to this problem: uncatalyzed is analyzed, understanding derived applied reaction. Evaluation previous mechanistic proposals from chemical perspective suggests that proton abstraction attacking water by general base stabilization charge development on gamma-phosphoryl oxygen atoms would not be catalytic. Rather, analysis focuses attention GDP leaving group, including beta-gamma bridge GTP, atom undergoes largest change in going ground state transition state. This leads new catalytic proposal which hydrogen bond backbone amide Gly-13 strengthened relative state, within an active site provides template complementary Strengthened interactions lysine, Lys-16, with beta-nonbridging phosphoryl oxygens network positions nucleophilic molecule group respect one another may also contribute catalysis. It speculated significant fraction GAP-activated GTPase activity arises additional interaction Arg side chain provided trans GAP. The conclusions for related G are expected apply more widely other enzymes catalyze (-PO(3)2-) transfer, kinases phosphatases.