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Urea's Effect on the Ribonuclease A Catalytic Efficiency: A Kinetic, (1)H NMR and Molecular Orbital Study.
MedLine Citation:
PMID:  23381689     Owner:  NLM     Status:  Publisher    
Understanding of protein-urea interactions is one of the greatest challenges to modern structural protein chemistry. Based in enzyme kinetics experiments and (1)H NMR spectroscopic analysis we proposed that urea, at low concentrations, directly interacts with the protonated histidines of the active center of RNase A, following a simple model of competitive inhibition. These results were supported by theoretical analysis based on the frontier molecular orbital theory and suggest that urea might establish a favorable interaction with the cationic amino acids. Our experimental evidence and theoretical analysis indicate that the initials steps of the molecular mechanism of Urea-RNase A interaction passes through the establishment of a three center four electron adduct. Also, our results would explain the observed disruption of the (1)H NMR signals corresponding to H12 and H119 (involved in catalysis) of the RNase A studied in the presence of urea. Our interaction model of urea-amino acids (cationic) can be extended to explain the inactivation of other enzymes with cationic amino acids at the active site.
Jorge Almarza; Luis Rincón; Alí Bahsas; María Angela Pinto; Francisco Brito
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-2-5
Journal Detail:
Title:  The protein journal     Volume:  -     ISSN:  1875-8355     ISO Abbreviation:  Protein J.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-2-5     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101212092     Medline TA:  Protein J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Laboratorio de Genética y Química Celular, Departamento de Biología, Facultad de Ciencias, Universidad de Los Andes, Mérida, Venezuela.
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