Adaptive response
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The adaptive response is a form of direct DNA repair in E. coli that is initiated against alkylation, particularly methylation, of guanine or thymine nucleotides or phosphate groups on the sugar-phosphate backbone of DNA. Under sustained exposure to low-level treatment with alkylating mutagens, E. coli can adapt to the presence of the mutagen, rendering subsequent treatment with high doses of the same agent less effective.[1]
The adaptive response is mediated by the ada protein, which covalently transfers alkyl groups from the damaged DNA to one of its two cysteine residues, rendering the protein enzymatically dead. It is thus a "suicide" protein that reacts stoichiometrically rather than catalytically. Methylated ada acts as a transcription factor to initiate the adaptive response, promoting the expression of related genes such as alkA, alkB, aidB, and ada itself. The alkA gene product is a glycosylase,[1] the aidB product is a flavin-containing protein,[1] and alkB is an iron-dependent oxidoreductase;[1] all are involved in further DNA repairs of alkylation damage.
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Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
