Active site and complete sequence of the suicidal methyltransferase that counters alkylation mutagenesis.

摘要: Abstract The inducible resistance to alkylation mutagenesis and killing in Escherichia coli (the adaptive response) is controlled by the ada gene. The Ada protein acts both as a positive regulator of response DNA repair enzyme, correcting premutagenic O6-alkylguanine suicidal transfer alkyl group one its own cysteine residues. We have determined sequence cloned ada+ gene regulatory region. data reveal potential sites autoregulation. Amino acid determinations show that active center for O6-methylguanine-DNA methyltransferase located close polypeptide COOH terminus has unusual -Pro-Cys-His-, preceded very hydrophobic These same structural features are present at site thymidylate synthase, suggesting common chemical mechanism activation cysteine.