Document Detail

Kinetic and structural analysis of alpha-D-Glucose-1-phosphate cytidylyltransferase from Salmonella typhi.
MedLine Citation:
PMID:  15634670     Owner:  NLM     Status:  MEDLINE    
Tyvelose is a 3,6-dideoxyhexose found in the O-antigen of the surface lipopolysaccharides of some pathogenic bacteria. It is synthesized via a complex biochemical pathway that is initiated by the formation of CDP-D-glucose. The production of this ligand is catalyzed by the enzyme glucose-1-phosphate cytidylyltransferase, which utilizes alpha-D-glucose 1-phosphate and MgCTP as substrates. Previous x-ray crystallographic investigations have demonstrated that the Salmonella typhi enzyme complexed with the product CDP-glucose is a fully integrated hexamer displaying 32 point group symmetry. The binding pocket for CDP-glucose is shared between two subunits. Here we describe both a detailed kinetic analysis of the cytidylyltransferase and a structural investigation of the enzyme complexed with MgCTP. These data demonstrate that the reaction catalyzed by the cytidylyltransferase proceeds via a sequential rather than a Bi Bi ping-pong mechanism as was previously reported. Additionally, the enzyme utilizes both CTP and UTP equally well as substrates. The structure of the enzyme with bound MgCTP reveals that the binding pocket for the nucleotide is contained within one subunit rather than shared between two. Key side chains involved in nucleotide binding include Thr(14), Arg(15), Lys(25), and Arg(111). In the previous structure of the enzyme complexed with CDP-glucose, those residues defined by Thr(14) to Ile(21) were disordered. The kinetic and x-ray crystallographic data presented here support a mechanism for this enzyme that is similar to that reported for the glucose-1-phosphate thymidylyltransferases.
Nicole M Koropatkin; W Wallace Cleland; Hazel M Holden
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.     Date:  2005-01-05
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  280     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2005 Mar 
Date Detail:
Created Date:  2005-03-14     Completed Date:  2005-04-25     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  10774-80     Citation Subset:  IM    
Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
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MeSH Terms
Arginine / chemistry
Binding Sites
Crystallography, X-Ray
Cytidine Triphosphate / chemistry
Diphosphates / chemistry
Lipopolysaccharides / chemistry
Lysine / chemistry
Models, Chemical
Models, Molecular
Nucleotidyltransferases / chemistry*
Protein Conformation
Salmonella typhi / chemistry,  enzymology*
Substrate Specificity
Threonine / chemistry
Grant Support
Reg. No./Substance:
0/Cations; 0/Diphosphates; 0/Ligands; 0/Lipopolysaccharides; 56-87-1/Lysine; 65-47-4/Cytidine Triphosphate; 72-19-5/Threonine; 74-79-3/Arginine; EC 2.7.7.-/Nucleotidyltransferases; EC cytidylyltransferase

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