Purification, crystallization and data collection of Pectobacterium chrysanthemi AcsD, a type A siderophore synthetase

AcsD, a type A siderophore synthetase with a molecular weight of 71 140 Da from Pectobacterium chrysanthemi, has been expressed, purified and crystallized at 293 K. The protein crystallized in the primitive orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 80.3, b = 95.7, c = 161.1 angstrom, alpha = beta = gamma = 90 degrees. Systematic absences were consistent with space group P2(1)2(1)2(1). A complete data set has been collected to 2.25 angstrom resolution on BM14 at the ESRF. Consideration of the likely solvent content suggested that the asymmetric unit contained two molecules. Gel-filtration experiments indicated that the protein was a dimer, although self-rotation analyses did not detect a convincing twofold symmetry axis in the asymmetric unit. The protein has no convincing sequence match to any known structure and thus solution is likely to require experimental phasing.