Crystallization and preliminary X-ray diffraction analysis of proline iminopeptidase from Xanthomonas campestris pv. citri

AbstractProline iminopeptidase from Xanthomonas campestris pv. citri, displaying no significant sequence homology to any protein previously analyzed by X-ray crystallography, has been crystallized using the vapour diffusion method. Two different orthorhombic crystal forms (space group C222 and I222) were obtained from a solution containing NaCl or polyethylene glycol monomethyl ether (MW 5000) as precipitating agent for the native and lanthanum-derivatized protein, respectively. Complete diffraction data sets have been collected up to 2.6 Å (native) and 3.0 Å (lanthanum derivative) resolution. Cell dimensions are a=147.2 Å, b=167.8 Å, and c=85.6 Å (C222) and a=146.7 Å, b=167.7 Å, and c=171.4 Å (I222), respectively. Considerations of the possible values of Vm and analysis of the self-rotation function of the native crystals account for the presence of one dimer per asymmetric unit, whereas a tetramer probably would occupy the smallest crystallographically independent crystal portion in the lanthanum-derivatized protein crystals