1vyr
|
STUCTURE OF PENTAERYTHRITOL TETRANIRATE REDUCTASE COMPLEXED WITH PICRIC ACID
OverviewOverview
The structure of pentaerythritol tetranitrate (PETN) reductase in complex, with the nitroaromatic substrate picric acid determined previously at 1.55, A resolution indicated additional electron density between the indole ring, of residue Trp-102 and the nitro group at C-6 of picrate. The data, suggested the presence of an unusual bond between substrate and the, tryptophan side chain. Herein, we have extended the resolution of the PETN, reductase-picric acid complex to 0.9 A. This high-resolution analysis, indicates that the active site is partially occupied with picric acid and, that the anomalous density seen in the original study is attributed to the, population of multiple conformational states of Trp-102 and not a formal, covalent bond between the indole ring of Trp-102 and picric acid. The, significance of any interaction between Trp-102 and nitroaromatic, substrates was probed further in solution and crystal complexes with, wild-type and mutant (W102Y and W102F) enzymes. Unlike with wild-type, enzyme, in the crystalline form picric acid was bound at full occupancy in, the mutant enzymes, and there was no evidence for multiple conformations, of active site residues. Solution studies indicate tighter binding of, picric acid in the active sites of the W102Y and W102F enzymes. Mutation, of Trp-102 does not impair significantly enzyme reduction by NADPH, but, the kinetics of decay of the hydride-Meisenheimer complex are accelerated, in the mutant enzymes. The data reveal that decay of the, hydride-Meisenheimer complex is enzyme catalyzed and that the final, distribution of reaction products for the mutant enzymes is substantially, different from wild-type enzyme. Implications for the mechanism of high, explosive degradation by PETN reductase are discussed.
About this StructureAbout this Structure
1VYR is a Single protein structure of sequence from Enterobacter cloacae with FMN and TNF as ligands. Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Atomic resolution structures and solution behavior of enzyme-substrate complexes of Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase. Multiple conformational states and implications for the mechanism of nitroaromatic explosive degradation., Khan H, Barna T, Harris RJ, Bruce NC, Barsukov I, Munro AW, Moody PC, Scrutton NS, J Biol Chem. 2004 Jul 16;279(29):30563-72. Epub 2004 May 5. PMID:15128738
Page seeded by OCA on Mon Nov 5 12:24:31 2007