Document Detail

Computer modelling studies on the mechanism of action of ribonuclease T1.
MedLine Citation:
PMID:  1741959     Owner:  NLM     Status:  MEDLINE    
The mechanism of action of ribonuclease (RNase) T1 is still a matter of considerable debate as the results of x-ray, 2-D nmr and site-directed mutagenesis studies disagree regarding the role of the catalytically important residues. Hence computer modelling studies were carried out by energy minimisation of the complexes of RNase T1 and some of its mutants (His40Ala, His40Lys, and Glu58Ala) with the substrate guanyl cytosine (GpC), and of native RNase T1 with the reaction intermediate guanosine 2',3'-cyclic phosphate (G greater than p). The puckering of the guanosine ribose moiety in the minimum energy conformer of the RNase T1-GpC (substrate) complex was found to be O4'-endo and not C3'-endo as in the RNase T1-3'-guanylic acid (inhibitor/product) complex. A possible scheme for the mechanism of action of RNase T1 has been proposed on the basis of the arrangement of the catalytically important amino acid residues His40, Glu58, Arg77, and His92 around the guanosine ribose and the phosphate moiety in the RNase T1-GpC and RNase T1-G greater than p complexes. In this scheme, Glu58 serves as the general base group and His92 as the general acid group in the transphosphorylation step. His40 may be essential for stabilising the negatively charged phosphate moiety in the enzyme-transition state complex.
P V Balaji; W Saenger; V S Rao
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of biomolecular structure & dynamics     Volume:  9     ISSN:  0739-1102     ISO Abbreviation:  J. Biomol. Struct. Dyn.     Publication Date:  1991 Oct 
Date Detail:
Created Date:  1992-01-16     Completed Date:  1992-01-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8404176     Medline TA:  J Biomol Struct Dyn     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  215-31     Citation Subset:  IM    
Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
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MeSH Terms
Amino Acids / chemistry
Computer Simulation
Hydrogen Bonding
Models, Molecular
Protein Conformation
Ribonuclease T1 / chemistry*
Reg. No./Substance:
0/Amino Acids; EC T1

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