MF7000837 OHR (Pseudomonas aeruginosa) 1n2f X-ray 2.01 Homodimer Pseudomonas aeruginosa 12485986 Lesniak J, Barton WA, Nikolov DB EMBO J. 2002 24 21 6649-59 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. GO:0006979 response to oxidative stress 2 1 Homooligomeric enzymes Homodimeric enzymes All chains according to the most probable oligomerization state stored in PDBe were considered. A Organic hydroperoxide resistance protein Pseudomonas aeruginosa Q9HZZ3 1 142 100% MQTIKALYTATATATGGRDGRAVSSDGVLDVKLSTPRELGGQGGAATNPEQLFAAGYSACFIGALKFVAGQRKQTLPADASITGKVGIGQIPGGFGLEVELHINLPGLEREAAEALVAAAHQVCPYSNATRGNIDVRLNVSV 142 secondary structure helix 36 40 secondary structure helix 48 73 secondary structure helix 109 124 secondary structure helix 124 131 secondary structure strand 8 15 secondary structure strand 20 24 secondary structure strand 30 33 secondary structure strand 81 91 secondary structure strand 94 104 secondary structure strand 135 141 pfam PF02566 OsmC-like protein 44 138 B Organic hydroperoxide resistance protein Pseudomonas aeruginosa Q9HZZ3 1 142 100% MQTIKALYTATATATGGRDGRAVSSDGVLDVKLSTPRELGGQGGAATNPEQLFAAGYSACFIGALKFVAGQRKQTLPADASITGKVGIGQIPGGFGLEVELHINLPGLEREAAEALVAAAHQVCPYSNATRGNIDVRLNVSV 142 secondary structure helix 36 40 secondary structure helix 48 73 secondary structure helix 109 124 secondary structure helix 124 130 secondary structure strand 6 15 secondary structure strand 20 24 secondary structure strand 30 33 secondary structure strand 81 91 secondary structure strand 94 104 secondary structure strand 136 141 pfam PF02566 OsmC-like protein 44 138 Direct evidence The full structure participates in mutual synergistic folding. OsmC-like protein Ohr is a tightly folded homodimer with a large buried hydrophobic surface area. The two monomers are tightly wrapped around each other in a head-to-tail orientation. Dimerization is dominated by helix–helix packing interactions of two long helices at the center of the hydrophobic core of the dimeric enzyme. Also, each β-sheet is composed of six strands, three from one monomer and three from the other (beta sheet augmentation). The hydrophobic core, as well as the surrounding β-sheets, are generated by combining elements of both monomers, therefore, it is clear that the two polypeptide chains have to fold together to form active Ohr, and that each monomer would individually be unstable. The two active sites are also located at the dimer interface (PMID:12485986). A N/A B N/A MF7000837 MF7000838 MF7000839 MF7000840 MF7000841 MF7000842 MF7000843