Crystallization and preliminary crystallographic analysis of the catalytic module of endolysin from Cp-7, a phage infecting Streptococcus pneumoniae.

As part of the life cycle of the pneumococcal phage Cp-7, the endolysin Cpl-7 cleaves the glycosidic beta1,4 bonds between N-acetylmuramic acid and N-acetylglucosamine in the pneumococcal cell wall, resulting in bacterial lysis. Recombinant Cpl-7 was overexpressed in Escherichia coli, purified and crystallized using the vapour-diffusion method at 291 K. Diffraction-quality tetragonal crystals of the catalytic module of Cpl-7 were obtained from a mixture of PEG 3350 and sodium formate. The crystals belonged to space group I422, with unit-cell parameters a = 127.93, b = 127.93, c = 82.07 A. Diffraction data sets were collected to 2.4 A resolution using a rotating-anode generator.