title: Mechanism of the chemical step for the guanosine triphosphate (GTP) hydrolysis catalyzed by elongation factor Tu.
abstract: Elongation factor Tu (EF-Tu), the protein responsible for delivering aminoacyl-tRNAs (aa-tRNAs) to ribosomal A site during translation, belongs to the group of guanosine-nucleotide (GTP/GDP) binding proteins. Its active 'on'-state corresponds to the GTP-bound form, while the inactive 'off'-state corresponds to the GDP-bound form. In this work we focus on the chemical step, GTP+H(2)O-->GDP+Pi, of the hydrolysis mechanism. We apply molecular modeling tools including molecular dynamics simulations and the combined quantum mechanical-molecular mechanical calculations for estimates of reaction energy profiles for two possible arrangements of switch II regions of EF-Tu. In the first case we presumably mimic binding of the ternary complex EF-Tu.GTP.aa-tRNA to the ribosome and allow the histidine (His85) side chain of the protein to approach the reaction active site. In the second case, corresponding to the GTP hydrolysis by EF-Tu alone, the side chain of His85 stays away from the active site, and the chemical reaction GTP+H(2)O-->GDP+Pi proceeds without participation of the histidine but through water molecules. In agreement with the experimental observations which distinguish rate constants for the fast chemical reaction in EF-Tu.GTP.aa-tRNA.ribosome and the slow spontaneous GTP hydrolysis in EF-Tu, we show that the activation energy barrier for the first scenario is considerably lower compared to that of the second case.
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory, 1/3, Moscow 119991, Russian Federation.
authors.forename: B L
authors.initials: BL
authors.lastname: Grigorenko
authors.forename: M S
authors.initials: MS
authors.lastname: Shadrina
authors.forename: I A
authors.initials: IA
authors.lastname: Topol
authors.forename: J R
authors.initials: JR
authors.lastname: Collins
authors.forename: A V
authors.initials: AV
authors.lastname: Nemukhin
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D006153:Guanosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D008956:Models, Chemical; D010444:Peptide Elongation Factor Tu / Q000737:chemistry* / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry* / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D012346:RNA, Transfer, Amino Acyl; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D010444:Peptide Elongation Factor Tu
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