Crystallization and preliminary X-ray diffraction studies of the peptide methionine sulfoxide reductase B domain of Neisseria meningitidis PILB.

Peptide methionine sulfoxide reductases (Msr) are ubiquitous enzymes that catalyse the reduction of free and protein-bound methionine sulfoxide back to methionine via sulfenic acid chemistry. Two classes of Msrs, MsrA and MsrB, have been described. The fact that the two Msrs display opposite stereoselectivities and have no sequence identity suggests that there is no structural similarity between the two classes. No three-dimensional structure of a MsrB is known. In the present report, the MsrB subdomain of Neisseria meningitidis PILB was used to grow orthorhombic crystals by the hanging-drop vapour-diffusion technique. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 44.0, b = 118.6, c = 138.5 A. Crystals of selenomethionine-substituted MsrB were grown under the same conditions in order to use the MAD method for structure determination. Three diffraction data sets at 1.8 A resolution were collected. The positions of the Se atoms were determined and should result in a full structure determination.