2abb

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spinqualitylabelsall models 2abb, resolution 1.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure of PETN reductase Y186F in complex with cyanide

Overview

The roles of His181, His184 and Tyr186 in PETN reductase have been, examined by mutagenesis, spectroscopic and stopped-flow kinetics, and by, determination of crystallographic structures for the Y186F PETN reductase, and reduced wild-type enzyme-progesterone complex. Residues His181 and, His184 are important in the binding of coenzyme, steroids, nitroaromatic, ligands and the substrate 2-cyclohexen-1-one. The H181A and H184A enzymes, retain activity in reductive and oxidative half-reactions, and thus do not, play an essential role in catalysis. Ligand binding and catalysis is not, substantially impaired in Y186F PETN reductase, which contrasts with data, for the equivalent mutation (Y196F) in Old Yellow Enzyme. The structure of, Y186F PETN reductase is identical to wild-type enzyme, with the obvious, exception of the mutation. We show in PETN reductase that Tyr186 is not a, key proton donor in the reduction of alpha/beta unsaturated carbonyl, compounds. The structure of two electron-reduced PETN reductase bound to, the inhibitor progesterone mimics the catalytic enzyme-steroid substrate, complex and is similar to the structure of the oxidized enzyme-inhibitor, complex. The reactive C1-C2 unsaturated bond of the steroid is, inappropriately orientated with the flavin N5 atom for hydride transfer., With steroid substrates, the productive conformation is achieved by, orientating the steroid through flipping by 180 degrees , consistent with, known geometries for hydride transfer in flavoenzymes. Our data highlight, mechanistic differences between Old Yellow Enzyme and PETN reductase and, indicate that catalysis requires a metastable enzyme-steroid complex and, not the most stable complex observed in crystallographic studies.

About this Structure

2ABB is a Single protein structure of sequence from Enterobacter cloacae with , and as ligands. Full crystallographic information is available from OCA.

Reference

Proton transfer in the oxidative half-reaction of pentaerythritol tetranitrate reductase. Structure of the reduced enzyme-progesterone complex and the roles of residues Tyr186, His181, His184., Khan H, Barna T, Bruce NC, Munro AW, Leys D, Scrutton NS, FEBS J. 2005 Sep;272(18):4660-71. PMID:16156787

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