A model for DNA binding and enzyme action derived from crystallographic studies of the TaqI N6-adenine-methyltransferase.
The crystal structures of the DNA-N6-adenine-methyltransferase M.TaqI, in complexes with the cofactor S-adenosyl-L-methionine (AdoMet) and the competitive inhibitor sinefungin (Sf) show identical folding of the polypeptide chains into two domains. The N-terminal domain carries the cofactor-binding site, the C-terminal domain is thought to be implicated in sequence-specific DNA binding. Model building of the M.TaqI-DNA complex suggests that the adenine to be methylated swings out of the double helix as found previously in the cytosine-C5-MTase HhaI DNA co-crystal structure. A torsion of the methionine moiety of the cofactor is required to bring the methyl group within reach of the swung-out base and allow methyl group transfer.
Schluckebier
G
G
Freie Universität Berlin, Institut für Kristallographie, Germany.
Labahn
J
J
Granzin
J
J
Schildkraut
I
I
Saenger
W
W
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D005998:Glycine; D008715:Methionine; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012436:S-Adenosylmethionine / Q000378:metabolism; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000737:chemistry* / Q000378:metabolism*
D004268:DNA-Binding Proteins; D012436:S-Adenosylmethionine; D004247:DNA; D008715:Methionine; C059680:DNA modification methylase TaqI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D005998:Glycine