Phylogeny of DNA Methyltransferases recognizing GATC and related DNA sequences.

Richard D. Morgan1, New England Bioloabs

DNA modification plays important roles in gene expression, DNA repair and in host protection in restriction systems. Many prokaryotes utilize methyltransferases that modify 5'-GATC-3' or 5'-GANTC-3' for these functions. Methyltransferases that modify the adenine residue of these sequences are close homologs, sharing very similar amino acid sequences even in the putative DNA recognition loop. We are investigating the phylogeny of these enzymes to discover how the variation in DNA sequence recognized has evolved. We hope to predict structurally how these very similar proteins discriminate between very similar DNA sequences. We also hope to predict how to evolve in vitro these enzyme such that they specifically recognize a different DNA sequence.