The SfaNI restriction-modification system from Enterococcus faecalis NEB215 is located on a putative mobile genetic element.

Abstract

A type IIS restriction-modification (R-M) system SfaNI from Enterococcus faecalis NEB215 has been characterized. The sfaNIM gene was cloned by the methylase selection method. Methyltransferase SfaNI, a protein of 695 amino acids, consists of two domains responsible for different DNA-strand recognition and modification, and a putative DNA-binding HTH domain located in the N-terminal part of the protein. The sfaNIR gene, located adjacent to the gene of the cognate modification methyltransferases, encodes a protein of 648 amino acids. The enzyme has been purified to apparent homogeneity and its biochemical characteristics have been described. The R-M system SfaNI is flanked by a transposase gene at its 5′ end, and a cassette chromosome recombinase ( ccr) gene complex, encoding serine recombinases CcrA and CcrB, at the 3′ end. Both proteins are specifically involved in genome rearrangement and are widely distributed among staphylococcal species. These results suggested that the R-M system SfaNI is present on the putative mobile element.