Purification, circular dichroism analysis, crystallization and preliminary X-ray diffraction analysis of the F plasmid CcdB killer protein.

Large crystals of the Escherichia coli F plasmid CcdB killer protein were grown from solutions containing 32% ammonium sulphate. The crystals belong to space group P4(2)2(1)2 with a = b = 104.52 A and c = 88.45 A or P2(1)2(1)2(1) with a = 77.62 A, b = 93.28 A and c = 141.44 A. Both crystal forms diffract to 2.6 A resolution. Structure determination by multiple isomorphous replacement is under way.