CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION ANALYSIS OF PROLINEIMINOPEPTIDASE FROM XANTHOMONAS-CAMPESTRIS PV CITRI

Proline iminopeptidase from Xanthomonas campestris pv. citri, displayi ng no significant sequence homology to any protein previously analyzed by X-ray crystallography, has been crystallized using the vapour diff usion method. Two different orthorhombic crystal forms (space group C2 22 and I222) were obtained from a solution containing NaCl or polyethy lene glycol monomethyl ether (MW 5000) as precipitating agent for the native and lanthanum-derivatized protein, respectively. Complete diffr action data sets have been collected up to 2.6 Angstrom (native) and 3 .0 Angstrom (lanthanum derivative) resolution. Cell dimensions are a = 147.2 Angstrom, b = 167.8 Angstrom, and 85.6 Angstrom (C222) and a = 146.7 Angstrom, b = 167.7 Angstrom, and c = 171.4 Angstrom, (I222), re spectively. Considerations of the possible values of V-m and analysis of the self-rotation function of the native crystals account for the p resence of one dimer per asymmetric unit, whereas a tetramer probably would occupy the smallest crystallographically independent crystal por tion in the lanthanum-derivatized protein crystals.