PDBsum entry 1n2f

Oxidoreductase

PDB id: 1n2f

Contents

Protein chains

142 a.a. *

Ligands

DTT ×2

Waters ×170

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Structural and functional characterization of the pseudomonas hydroperoxide resistance protein ohr.

Authors

J.Lesniak, W.A.Barton, D.B.Nikolov.

Ref.

EMBO J, 2002, 21, 6649-6659. [DOI no: 10.1093/emboj/cdf670]

PubMed id

12485986

Abstract

Bacteria have developed complex strategies to detoxify and repair damage caused by reactive oxygen species. These compounds, produced during bacterial aerobic respiration as well as by the host immune system cells as a defense mechanism against the pathogenic microorganisms, have the ability to damage nucleic acids, proteins and phospholipid membranes. Here we describe the crystal structure of Pseudomonas aeruginosa Ohr, a member of a recently discovered family of organic hydroperoxide resistance proteins. Ohr is a tightly folded homodimer, with a novel alpha/beta fold, and contains two active sites located at the monomer interface on opposite sides of the molecule. Using in vitro assays, we demonstrate that Ohr functions directly as a hydroperoxide reductase, converting both inorganic and organic hydroperoxides to less toxic metabolites. Site-directed mutagenesis confirms that the two conserved cysteines in each active site are essential for catalytic activity. We propose that the Ohr catalytic mechanism is similar to that of the structurally unrelated peroxiredoxins, directly utilizing highly reactive cysteine thiol groups to elicit hydroperoxide reduction.

Figure 2.
Figure 2 (A–C) Structure of the Ohr dimer. One monomer is in red, the other is in blue. Three 90° views of the Ohr dimer bound to DTT. (D) Structure of the Ohr monomer depicting the two domains (the N-terminal subdomain is shown in red and the C-terminal subdomain is shown in blue) and a DTT molecule. DTT is shown in CPK format, with oxygen atoms in red, carbon atoms in black and sulfur atoms in yellow.

Figure 3.
Figure 3 (A) Molecular surface rendering of the Ohr dimer. The catalytically active Cys60 (shown in yellow) lies at the bottom of the active-site pocket, which is outlined with hydrophobic residues (shown in green). (B) Stereo view of the Ohr active site. Hydrogen bonds are depicted by light blue, dashed lines. Monomer A (shown in green) contributes Cys60 and Cys124 residues (also in green) and monomer B (shown in purple) contributes Arg18 and Glu50 residues (also in purple) to the active site. The DTT molecule (orange) is depicted in a ball-and-stick format. Nitrogen atoms are dark blue, oxygen atoms are red and sulfur atoms are yellow. (C) Representative region of the density-modified experimental electron density map showing the active-site pocket in the Ohr structure (the refined model) contoured at 1.5 .

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: EMBO J (2002, 21, 6649-6659) copyright 2002.