title: Differential binding of S-adenosylmethionine S-adenosylhomocysteine and Sinefungin to the adenine-specific DNA methyltransferase M.TaqI.
abstract: The crystal structures of the binary complexes of the DNA methyltransferase M.TaqI with the inhibitor Sinefungin and the reaction product S-adenosyl-L-homocysteine were determined, both at 2.6 A resolution. Structural comparison of these binary complexes with the complex formed by M.TaqI and the cofactor S-adenosyl-L-methionine suggests that the key element for molecular recognition of these ligands is the binding of their adenosine part in a pocket, and discrimination between cofactor, reaction product and inhibitor is mediated by different conformations of these molecules; the methionine part of S-adenosyl-L-methionine is located in the binding cleft, whereas the amino acid moieties of Sinefungin and S-adenosyl-L-homocysteine are in a different orientation and interact with the active site amino acid residues 105NPPY108. Dissociation constants for the complexes of M.TaqI with the three ligands were determined spectrofluorometrically. Sinefungin binds more strongly than S-adenosyl-L-homocysteine or S-adenosyl-L-methionine, with KD=0.34 microM, 2.4 microM and 2.0 microM, respectively.
authors.affiliation: Institut für Kristallographie Freie Universität Berlin, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schluckebier
authors.forename: M
authors.initials: M
authors.lastname: Kozak
authors.forename: N
authors.initials: N
authors.lastname: Bleimling
authors.forename: E
authors.initials: E
authors.lastname: Weinhold
authors.forename: W
authors.initials: W
authors.lastname: Saenger
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011487:Protein Conformation; D012435:S-Adenosylhomocysteine / Q000737:chemistry / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism*; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D004791:Enzyme Inhibitors; D008024:Ligands; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; C059680:DNA modification methylase TaqI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D000241:Adenosine; C006235:sinefungin