Crystallization and preliminary X-ray crystallographic analysis of ImmE7 protein of colicin E7.

The ImmE7 protein, which can bind specifically to the DNase colicin E7 and neutralize its bactericidal activity, has been purified and crystallized in two different crystal forms by vapor diffusion method. The orthorhombic crystals belong to space group I222 or I2(1)2(1)2(1) and have unit cell dimensions a = 75.1 A, b = 50.5 A, and c = 45.4 A. The second form is monoclinic space group P2(1) with cell dimensions a = 29.3 A, b = 102.7 A, c = 53.0 A, and beta = 91.5 degrees. The orthorhombic crystals diffract to 1.8 A resolution, and are suitable for high-resolution X-ray analysis.