Alw26l,Eco31l andEsp3l-type Ils methyltransferases modifying cytosine and adenine in complementary strands of the target DNA

The specificity of three DNA methyltransferases M.Alw26I, M.Eco31I and M.Esp3I, isolated from Acinetobacter Iwoffi RFL26, Escherichia coli RFL31 and Hafnia alvei RFL3+, respectively, was determined. All the enzymes methylate both strands of asymmetric recognition sites yielding m5C in the top-strand and m6A in the bottom-strand, as below: 5'-GTm5CTC 5'-GGTm5CTC 5'-CGTm5CTC 3'-Cm6AGAG 3'-CCm6AGAG 3'-GCm6AGAG (M.Alw26I) (M.Eco31I) (M.Esp3I) They are the first members of type IIs methyltransferases that modify different types of nucleotides in the recognition sequence.