1sto
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(New page: 200px<br /><applet load="1sto" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sto, resolution 2.6Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 00:32, 21 November 2007
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CRYSTAL STRUCTURE OF OROTATE PHOSPHORIBOSYLTRANSFERASE
Overview
Phosphoribosyltransferases (PRTases) are enzymes involved in the synthesis, of purine, pyrimidine, and pyridine nucleotides. They utilize, alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP) and a nitrogenous base to, form a beta-N-riboside monophosphate and pyrophosphate (PPi), and their, functional significance in nucleotide homeostasis is evidenced by the, devastating effects of inherited diseases associated with the decreased, activity and/or stability of these enzymes. The 2.6-A structure of the, Salmonella typhimurium orotate phosphoribosyltransferase (OPRTase), complexed with its product orotidine monophosphate (OMP) provides the, first detailed image of a member of this group of enzymes. The OPRTase, three-dimensional structure was solved using multiple isomorphous, replacement methods and reveals two major features: a core five-stranded, alpha/beta twisted sheet and an N-terminal region that partially covers, the C-terminal portion of the core. PRTases show a very high degree of, base specificity. In OPRTase, this is determined by steric constraints and, the position of hydrogen bond donors/acceptors of a solvent-inaccessible, crevice where the orotate ring of bound OMP resides. Crystalline OPRTase, is a dimer, with catalytically important residues from each subunit, available to the neighboring subunit, suggesting that oligomerization is, necessary for its activity. On the basis of the presence of a common PRPP, binding motif among PRTases and the similar chemistry these enzymes, perform, we propose that the alpha/beta core found in OPRTase will, represent a common feature for PRTases. This generality is demonstrated by, construction of a model of the human hypoxanthine-guanine, phosphoribosyltransferase (HGPRTase) from secondary structure predictions, for HGPRTase and the three-dimensional structure of OPRTase.
About this Structure
1STO is a Single protein structure of sequence from Salmonella typhimurium with OH and OMP as ligands. Active as Orotate phosphoribosyltransferase, with EC number 2.4.2.10 Full crystallographic information is available from OCA.
Reference
Crystal structure of orotate phosphoribosyltransferase., Scapin G, Grubmeyer C, Sacchettini JC, Biochemistry. 1994 Feb 15;33(6):1287-94. PMID:8312245
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