Crystallization and preliminary X-ray analysis of Mlc from Escherichia coli.

Mlc is a prokaryotic transcriptional repressor controlling the expression of a number of genes encoding enzymes of the Escherichia coli phosphotransferase system (PTS), ptsG and manXYZ, the specific enzyme II for glucose and mannose PTS transporters, as well as malT, the gene of the global activator of the mal regulon. The mlc gene has been cloned into a pQE vector and recombinant protein with the point mutation R52H was expressed and purified as the selenomethionine-labelled derivative. Crystallization of SeMet-Mlc R52H was carried out using the vapour-diffusion method. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 235.95, b = 74.71, c = 154.95 A, beta = 129.15 degrees, and diffract to 2.9 A resolution.