1jyl
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(New page: 200px<br /><applet load="1jyl" size="450" color="white" frame="true" align="right" spinBox="true" caption="1jyl, resolution 2.4Å" /> '''Catalytic Mechanism o...)
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Revision as of 22:19, 24 November 2007
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Catalytic Mechanism of CTP:phosphocholine Cytidylytransferase from Streptococcus pneumoniae (LicC)
Overview
Pneumococcal LicC is a member of the nucleoside triphosphate transferase, superfamily and catalyzes the transfer of a cytidine monophosphate from, CTP to phosphocholine to form CDP-choline. The structures of apo-LicC and, the LicC-CDP-choline-Mg(2+) ternary complex were determined, and the, comparison of these structures reveals a significant conformational change, driven by the multivalent coordination of Mg(2+). The key event is, breaking the Glu(216)-Arg(129) salt bridge, which triggers the coalescence, of four individual beta-strands into two extended beta-sheets. These, movements reorient the side chains of Trp(136) and Tyr(190) for the, optimal binding and alignment of the phosphocholine moiety. Consistent, with these conformational changes, LicC operates via a compulsory ordered, kinetic mechanism. The structures explain the substrate specificity of, LicC for CTP and phosphocholine and implicate a direct role for Mg(2+) in, aligning phosphocholine for in-line nucleophilic attack and stabilizing, the negative charge that develops in the pentacoordinate transition state., These results provide a structural basis for assigning a specific role for, magnesium in the catalytic mechanism of pneumococcal LicC.
About this Structure
1JYL is a Single protein structure of sequence from Streptococcus pneumoniae with MG and CDC as ligands. Full crystallographic information is available from OCA.
Reference
Structure and mechanism of CTP:phosphocholine cytidylyltransferase (LicC) from Streptococcus pneumoniae., Kwak BY, Zhang YM, Yun M, Heath RJ, Rock CO, Jackowski S, Park HW, J Biol Chem. 2002 Feb 8;277(6):4343-50. Epub 2001 Nov 12. PMID:11706035
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