Allosteric and catalytic binding of S-adenosylmethionine to Escherichia coli DNA adenine methyltransferase monitored by 3H NMR.

Adenine methylation of GATC sequences in DNA is carried out by the DNA adenine methyltransferase with the methyl group source being the cofactor S-adenosylmethionine. We report 3H NMR studies on the interaction of DNA adenine methyltransferase with S-adenosylmethionine and the reaction when the ternary complex is formed with an oligonucleotide containing a GATC site. The methylation reaction was also studied in the presence of a competitive inhibitor and this showed two successive stages involved in the methylation and two sites of binding for S-adenosylmethionine.