Three-dimensional structure of the adenine-specific DNA methyltransferase M.Taq I in complex with the cofactor S-adenosylmethionine.
The Thermus aquaticus DNA methyltransferase M.Taq I (EC 2.1.1.72) methylates N6 of adenine in the specific double-helical DNA sequence TCGA by transfer of --CH3 from the cofactor S-adenosyl-L-methionine. The x-ray crystal structure at 2.4-A resolution of this enzyme in complex with S-adenosylmethionine shows alpha/beta folding of the polypeptide into two domains of about equal size. They are arranged in the form of a C with a wide cleft suitable to accommodate the DNA substrate. The N-terminal domain is dominated by a nine-stranded beta-sheet; it contains the two conserved segments typical for N-methyltransferases which form a pocket for cofactor binding. The C-terminal domain is formed by four small beta-sheets and alpha-helices. The three-dimensional folding of M.Taq I is similar to that of the cytosine-specific Hha I methyltransferase, where the large beta-sheet in the N-terminal domain contains all conserved segments and the enzymatically functional parts, and the smaller C-terminal domain is less structured.
Institut für Kristallographie, Freie Universität, Berlin, Germany.
J
J
Labahn
J
J
Granzin
G
G
Schluckebier
D P
DP
Robinson
W E
WE
Jack
I
I
Schildkraut
W
W
Saenger
D001426:Bacterial Proteins / Q000648:ultrastructure; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D012436:S-Adenosylmethionine / Q000737:chemistry; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000648:ultrastructure*; D013824:Thermus / Q000201:enzymology
D001426:Bacterial Proteins; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D012436:S-Adenosylmethionine; D004247:DNA; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)