Crystallization and preliminary X-ray diffraction studies of the peptide methionine sulfoxide reductase from Escherichia coli

Peptide methionine sulfoxide reductase mediates the reduction of protein sulfoxide methionyl residues back to methionines and could thus be implicated in the antioxidant defence of organisms. Hexagonal crystals of the Escherichia coli enzyme (MsrA) were obtained by the hanging‐drop vapour‐diffusion technique. They belong to space group P6522, with unit‐cell parameters a = b = 102.5, c = 292.3 Å, γ = 120°. A native data set was collected at 1.9 Å resolution. Crystals of selenomethionine‐substituted MsrA were also grown under the same crystallization conditions. A three‐wavelength MAD experiment has led to the elucidation of the positions of the Se atoms and should result in a full structure determination.