Document Detail


A remote mutation affects the hydride transfer by disrupting concerted protein motions in thymidylate synthase.
MedLine Citation:
PMID:  23034004     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The role of protein flexibility in enzyme-catalyzed activation of chemical bonds is an evolving perspective in enzymology. Here we examine the role of protein motions in the hydride transfer reaction catalyzed by thymidylate synthase (TSase). Being remote from the chemical reaction site, the Y209W mutation of Escherichia coli TSase significantly reduces the protein activity, despite the remarkable similarity between the crystal structures of the wild-type and mutant enzymes with ligands representing their Michaelis complexes. The most conspicuous difference between these two crystal structures is in the anisotropic B-factors, which indicate disruption of the correlated atomic vibrations of protein residues in the mutant. This dynamically altered mutant allows a variety of small thiols to compete for the reaction intermediate that precedes the hydride transfer, indicating disruption of motions that preorganize the protein environment for this chemical step. Although the mutation causes higher enthalpy of activation of the hydride transfer, it only shows a small effect on the temperature dependence of the intrinsic KIE, suggesting marginal changes in the geometry and dynamics of the H-donor and -acceptor at the tunneling ready state. These observations suggest that the mutation disrupts the concerted motions that bring the H-donor and -acceptor together during the pre- and re-organization of the protein environment. The integrated structural and kinetic data allow us to probe the impact of protein motions on different time scales of the hydride transfer reaction within a complex enzymatic mechanism.
Authors:
Zhen Wang; Thelma Abeysinghe; Janet S Finer-Moore; Robert M Stroud; Amnon Kohen
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-10-15
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  134     ISSN:  1520-5126     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-24     Completed Date:  2013-03-28     Revised Date:  2013-10-30    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  17722-30     Citation Subset:  IM    
Affiliation:
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242-1727, USA.
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MeSH Terms
Descriptor/Qualifier:
Biocatalysis
Crystallography, X-Ray
Escherichia coli / enzymology*
Kinetics
Models, Molecular
Molecular Structure
Mutation
Thymidylate Synthase / chemistry,  genetics,  metabolism*
Grant Support
ID/Acronym/Agency:
GM065368/GM/NIGMS NIH HHS; GM51232/GM/NIGMS NIH HHS; R01 GM065368/GM/NIGMS NIH HHS
Chemical
Reg. No./Substance:
EC 2.1.1.45/Thymidylate Synthase
Comments/Corrections

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