title: Site directed mutagenesis of two cysteine residues in the E. coli ogt O6-alkylguanine DNA alkyltransferase protein.
abstract: The E. coli ogt O6-alkylguanine-DNA alkyltransferase has two cysteine residues positioned identically with respect to cysteines in the E. coli ada O6-alkylguanine-DNA alkyltransferase. In order to assess their function, these residues were each substituted by a glycine to generate altered forms of the ogt protein. Mutagenesis of cysteine-139, located within a 'PCHRV' region of homology, eliminated functional activity confirming that this residue is the methyl-accepting cysteine in the active site of the protein. Substitution of cysteine 102 within the sequence 'LRTIPCG' had little effect on the ogt protein activity demonstrating that this cysteine is not directly involved with the transfer of O6-methylguanine adducts.
authors.affiliation: CRC Department of Chemical Carcinogenesis, Paterson Institute for Cancer Research, Christie Hospital and Holt Radium Institute, Manchester, UK.
authors.forename: L C
authors.initials: LC
authors.lastname: Harris
authors.forename: P M
authors.initials: PM
authors.lastname: Potter
authors.forename: G P
authors.initials: GP
authors.lastname: Margison
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D003545:Cysteine / Q000235:genetics*; D004274:DNA, Recombinant; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D007700:Kinetics; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019853:O(6)-Methylguanine-DNA Methyltransferase; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D004274:DNA, Recombinant; D011993:Recombinant Fusion Proteins; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D003545:Cysteine