Four new type I restriction enzymes identified in Escherichia coli clinical isolates

Using a plasmid transformation method and the RM search computer program, four type I restriction enzymes with new recognition sites and two isoschizomers (EcoBI and Eco3771) were identified in a collection of clinical Escherichia coli isolates. These new enzymes were designated Eco3941, Eco8261, Eco851l and Eco912l. Their recognition sequences were determined to be GAC(5N)RTAAY, GCA(6N)CTGA, GTCA(6N)TGAY and CAC(SN)TGGC, respectively. A methylation sensitivity assay, using various synthetic oligonucleotides, was used to identify the adenines that prevent cleavage when methylated (underlined). These results suggest that type I enzymes are abundant in E.coli and many other bacteria, as has been inferred from bacterial genome sequencing projects.