Isolation and characterization of the M.EaeI modification methylase.

The modification enzyme (M.EaeI) corresponding to the restriction endonuclease EaeI was partially purified from Enterobacter aerogenes PW201. The M.EaeI enzyme methylates the innermost cytosine residue in each strand of the family of related sequences that constitute the EaeI recognition site to give: 5'-Y-G-G-5mC-C-R-3' where 5mC is 5-methylcytosine. M.EaeI protects these sites against cleavage by HaeIII, and protects overlapping 5'-C-C-G-G-3' sites against cleavage by both HpaII and MspI.