Overproduction and purification of McrC protein from Escherichia coli K-12.

The McrC protein, encoded by one of the two genes involved in the McrB restriction system, was produced in Escherichia coli cells by using a T7 expression system. Following sequential DEAE-Sepharose and hydroxylapatite column chromatography, the protein was purified to apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequence of the purified McrC protein agreed exactly with the one deduced from the DNA sequence by Ross et al. (J. Bacteriol. 171:1974-1981, 1989).