Methylation and cleavage sequences of the EcoP1 restriction-modification enzyme

EcoP1 is a restriction modification enzyme encoded by bacteriophage P1. It requires ATP for cleavage and S-adenosyl methionine for methylation of DNA. We have mapped the sites of both cleavage and methylation in simian virus 40 DNA and determined their sequences. The enzyme methylates the sequence A-G-mA-C-C and cuts the DNA 25 to 27 base-pairs from the site of methylation in the 3′ direction, with a two to four base-pair stagger between cuts. Consistent with the fact that the methylation sequence is asymmetric, the enzyme methylates only one strand in vitro. One variant of simian virus 40 has acquired an additional EcoP1 methylation and cleavage site by changing a A-G-A-A-C sequence to A-G-A-C-C.