Structure of the Bacillus subtilis OhrB hydroperoxide-resistance protein in a fully oxidized state.

The crystal structure of the fully oxidized form of the Bacillus subtilis organic hydroperoxide-resistance (OhrB) protein is reported at 2.1 A resolution. The electron density reveals an intact catalytic disulfide bond (Cys55-Cys119) in each of the two molecules, which are intertwined into a canonical obligate dimer. However, the stereochemistry of the disulfides is unorthodox and strained, suggesting that they are sensitive to reducing agents. A deep solvent-accessible gorge reaching Cys55 may represent the access route for the reductant.