title: Transition from nonspecific to specific DNA interactions along the substrate-recognition pathway of dam methyltransferase.
abstract: DNA methyltransferases methylate target bases within specific nucleotide sequences. Three structures are described for bacteriophage T4 DNA-adenine methyltransferase (T4Dam) in ternary complexes with partially and fully specific DNA and a methyl-donor analog. We also report the effects of substitutions in the related Escherichia coli DNA methyltransferase (EcoDam), altering residues corresponding to those involved in specific interaction with the canonical GATC target sequence in T4Dam. We have identified two types of protein-DNA interactions: discriminatory contacts, which stabilize the transition state and accelerate methylation of the cognate site, and antidiscriminatory contacts, which do not significantly affect methylation of the cognate site but disfavor activity at noncognate sites. These structures illustrate the transition in enzyme-DNA interaction from nonspecific to specific interaction, suggesting that there is a temporal order for formation of specific contacts.
authors.affiliation: Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Horton
authors.forename: Kirsten
authors.initials: K
authors.lastname: Liebert
authors.forename: Stanley
authors.initials: S
authors.lastname: Hattman
authors.forename: Albert
authors.initials: A
authors.lastname: Jeltsch
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Cheng
mesh_terms: D000225:Adenine / Q000737:chemistry; D000241:Adenosine / Q000031:analogs & derivatives / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017122:Bacteriophage T4 / Q000201:enzymology*; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D012435:S-Adenosylhomocysteine / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D014764:Viral Proteins
chemical_list: D029968:Escherichia coli Proteins; D009841:Oligonucleotides; D014764:Viral Proteins; D004247:DNA; D012435:S-Adenosylhomocysteine; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499297:dam protein, Bacteriophage T4; C499294:dam protein, E coli; D000225:Adenine; D000241:Adenosine; C006235:sinefungin