Crystallization and preliminary X-ray diffraction analysis of a recombinant cysteine-free mutant of crmA

CrmA is an unusual serpin that has a reactive-center loop one residue shorter than other members of the superfamily. Most interestingly, crmA has inhibitory activity against both cysteine and serine proteinases involved in the regulation of cell apoptosis. The three-dimensional structure of crmA will give insight into the mechanism that this serpin employs to inhibit both cysteine and the serine proteinases, as well as help to explain the significance of the shorter reactive-center loop. The monodisperse cysteine-free mutant of crmA was crystallized in the presence of phosphate salts. Crystals diffract to 2.90 Å and belong to space group P2₁2₁2₁, with unit-cell parameters a = 42.67, b = 93.15, c = 101.63 Å.