Crystallization and preliminary diffraction studies of native and selenomethionine CcmG (CycY, DsbE)

Disulfide-bond (Dsb) proteins are a family of redox proteins containing a C ys-X-X-Cys motif. They are essential for disulfide-bond exchange in the bac terial periplasm and are necessary for the correct folding and function of many secreted proteins. CcmG (DsbE) is a reducing Dsb protein required for cytochrome c maturation. Crystals of Bradyrhizobium japonicum CcmG have bee n obtained that diffract X-rays to 1.14 Angstrom resolution. The crystals a re orthorhombic, space group P2(1)2(1)2(1), with unit-cell parameters a = 3 5.1, b = 48.2, c = 90.2 Angstrom. Selenomethionine CcmG was expressed witho ut using a methionine auxotroph or methionine-pathway inhibition and was pu rified without reducing agents.