Purification, crystallization and preliminary X-ray analysis of Bacteroides fragilis Zn2+ beta-lactamase

The Zn(2+) beta-lactamase from Bacteroides fragilis (E.C. 3.5.2.6) was overexpressed in Escherichia coli using an isopropylthiogalactoside-inducible T7 RNA polymerase expression system. Crystallization trials by the hanging-drop vapour-diffusion method have yielded two different crystal forms from two slightly different conditions. Crystals of form I belong to the monoclinic space group C2 with unit-cell dimensions a = 56.03, b = 43.98, c = 105.32 A, beta = 112 degrees and diffracted only up to 4.0 A. Crystals of form II are orthorhombic, space group P2(1)2(1)2(1) with unit-cell dimensions a = 48.10, b = 98.05, c = 111.76 A, diffract to at least 2.0 A and are suitable for high-resolution structural analysis.