Alw26l, Eco31l and Esp3l-type ils methyltransferases modifying cytosine and adenine in complementary strands of the target DNA

Abstract

The specificity of three DNA methyltransferases M.Alw26l, M.Eco31l and M.Esp3l, Isolated from Aclnetobacter iwoffi RFL26, Eschertchia coll RFL31 and Hafnla alvel 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.Alw26l) (M.Eco31l) (M.Esp3l)They are the first members of type lls methyltransferases that modify different types of nucleotides in the recognition sequence. © 1992 Oxford University Press.