M.TaqI: possible catalysis via cation-pi interactions in N-specific DNA methyltransferases.
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.
Schluckebier
G
G
Institut für Kristallographie, Freie Universität Berlin, Germany.
Labahn
J
J
Granzin
J
J
Saenger
W
W
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
D002412:Cations; D004247:DNA; C059680:DNA modification methylase TaqI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D000225:Adenine