1a2n
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STRUCTURE OF THE C115A MUTANT OF MURA COMPLEXED WITH THE FLUORINATED ANALOG OF THE REACTION TETRAHEDRAL INTERMEDIATE
OverviewOverview
MurA (UDP-GlcNAc enolpyruvyl transferase), the first enzyme in bacterial, peptidoglycan biosynthesis, catalyzes the enolpyruvyl transfer from, phosphoenolpyruvate (PEP) to the 3'-OH of UDP-GlcNAc by an, addition-elimination mechanism that proceeds through a tetrahedral ketal, intermediate. The crystal structure of the Cys115-to-Ala (C115A) mutant of, Escherichia coli MurA complexed with a fluoro analogue of the tetrahedral, intermediate revealed the absolute configuration of the adduct and the, stereochemical course of the reaction. The fluorinated adduct was, generated in a preincubation of wild-type MurA with, (Z)-3-fluorophosphoenolpyruvate (FPEP) and UDP-GlcNAc and purified after, enzyme denaturation. The fluorine substituent stabilizes the tetrahedral, intermediate toward decomposition by a factor of 10(4)-10(6), facilitating, manipulation of the adduct. The C115A mutant of MurA was utilized to avoid, the microheterogeneity that arises in the wild-type MurA from the attack, of Cys115 on C-2 of FPEP in competition with the formation of the, fluorinated adduct. The crystal structure of the complex was determined to, 2.8 A resolution, and the absolute configuration at C-2 of the adduct was, found to be 2R. Thus, addition of the 3'-OH of UDP-GlcNAc is to the 2-si, face of FPEP, corresponding to the 2-re face of PEP. Given the previous, observation that, in D2O, the addition of D+ to C-3 of PEP proceeds from, the 2-si face [Kim, D. H., Lees, W. J., and Walsh, C. T. (1995) J. Am., Chem. Soc. 117, 6380-6381], the addition across the double bond of PEP is, anti. Also, because the overall stereochemical course has been shown to be, either anti/syn or syn/anti [Lees, W. J., and Walsh, C. T. (1995) J. Am., Chem. Soc. 117, 7329-7337], it now follows that the stereochemistry of, elimination of H+ from C-3 and Pi from C-2 of the tetrahedral intermediate, of the reaction is syn.
About this StructureAbout this Structure
1A2N is a Single protein structure of sequence from Escherichia coli with TET as ligand. Active as UDP-N-acetylglucosamine 1-carboxyvinyltransferase, with EC number 2.5.1.7 Full crystallographic information is available from OCA.
ReferenceReference
Stereochemical course of enzymatic enolpyruvyl transfer and catalytic conformation of the active site revealed by the crystal structure of the fluorinated analogue of the reaction tetrahedral intermediate bound to the active site of the C115A mutant of MurA., Skarzynski T, Kim DH, Lees WJ, Walsh CT, Duncan K, Biochemistry. 1998 Feb 24;37(8):2572-7. PMID:9485407
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