The cleavage sites and localization of genes encoding the restriction endonucleases Eco1831I and EcoHI.

The restriction endonucleases Eco1831I and EcoHI cleave before the first 5'-cytosine in the recognition sequence 5'-decreases CCSGG--3'/3'--GGSCC increases-5' (where S = G or C), generate 5-base 5' cohesive ends, and are encoded by homologous plasmids that are restricted in McrA+ hosts. Thus, they differ in their cleavage specificity from that of the BcnI isoschizomer, which cleaves after the second 5' cytosine.