Active site and complete sequence of the suicidal methyltransferase that counters alkylation mutagenesis.
AUTOR(ES)
Demple, B
RESUMO
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 the response and as a DNA repair enzyme, correcting premutagenic O6-alkylguanine in DNA by suicidal transfer of the alkyl group to one of its own cysteine residues. We have determined the DNA sequence of the cloned ada+ gene and its regulatory region. The data reveal potential sites of ada autoregulation. Amino acid sequence determinations show that the active center for the O6-methylguanine-DNA methyltransferase is located close to the polypeptide COOH terminus and has the unusual sequence -Pro-Cys-His-, preceded by a very hydrophobic region. These same structural features are present at the active site of thymidylate synthase, suggesting a common chemical mechanism for activation of the cysteine.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=397630Documentos Relacionados
- Identification of active-site residues in protease 3C of hepatitis A virus by site-directed mutagenesis.
- Search for the optimal sequence of the ribosome binding site by random oligonucleotide-directed mutagenesis.
- Determination of lysine residues affinity labeled in the active site of yeast RNA polymerase II(B) by mutagenesis.
- Active site amino acid sequence of the bovine O6-methylguanine-DNA methyltransferase.
- Analysis of the diphtheria tox promoter by site-directed mutagenesis.