title: M.TaqI: possible catalysis via cation-pi interactions in N-specific DNA methyltransferases.
abstract: The adenine-specific DNA methyltransferase M.TaqI transfers a methyl group from S-adenosylmethionine to N6 of the adenine residue in the DNA sequence 5'-TCGA-3'. In the crystal structure of M.TaqI in complex with S-adenosylmethionine the enzyme is folded into two domains: An N-terminal catalytic domain, whose fold is conserved among S-adenosyl-methionine dependent methyltransferases, and a DNA recognition domain which possesses a unique fold. In the active site, two aromatic residues, Tyr 108 and Phe 196, are postulated to bind the flipped-out target DNA adenine which becomes methylated. By lowering the energy of the positively charged transition state via cationic-pi interactions, these two residues probably hold a key role in catalysis.
authors.affiliation: Institut für Kristallographie, Freie Universität Berlin, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schluckebier
authors.forename: J
authors.initials: J
authors.lastname: Labahn
authors.forename: J
authors.initials: J
authors.lastname: Granzin
authors.forename: W
authors.initials: W
authors.lastname: Saenger
mesh_terms: D000225:Adenine / Q000378:metabolism; D002384:Catalysis; D002412:Cations; D004247:DNA / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002412:Cations; D004247:DNA; C059680:DNA modification methylase TaqI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D000225:Adenine