Crystallization and preliminary X-ray study of two crystal forms of Klebsiella oxytoca diol dehydratase-cyanocobalamin complex

Two crystal forms of Klebsiella oxytoca diol dehydratase complexed with cya nocobalamin have been obtained and preliminary crystallographic experiments have been performed. The crystals belong to two different space groups, de pending on the crystallization conditions. One crystal (form I) belongs to space group P2(1)2(1)2(1) with unit-cell parameters a = 76.2, b = 122.3, c = 209.6 Angstrom, and diffracts to 2.2 Angstrom resolution using an X-ray b eam from a synchrotron radiation source. The other crystal (form II) belong s to space group P2(1) with unit-cell parameters a = 75.4, b = 132.7, c = 2 98.8 Angstrom, beta = 91.9 degrees, and diffracts to 3.0 Angstrom resolutio n. For the purpose of structure determination, a heavy-atom derivative sear ch was carried out and some mercuric derivatives were found to be promising . Structure analysis by the multiple isomorphous replacement method is now under way.