title: AlkB mystery solved: oxidative demethylation of N1-methyladenine and N3-methylcytosine adducts by a direct reversal mechanism.
abstract: All organisms have multiple DNA repair pathways to protect against alkylation-induced mutation and cell death. For nearly two decades, we have known that the Escherichia coli alkB gene product protects against cell killing by S(N)2-alkylating agents, probably through DNA repair. Despite numerous attempts, a specific DNA repair activity could not be assigned to AlkB. Now, a breakthrough in biology and biochemistry, coupled with the discovery of an in silico protein structure, has uncovered a novel direct reversal DNA repair mechanism that is catalyzed by AlkB, namely the oxidative demethylation of N1-methyladenine or N3-methylcytosine DNA lesions. This reaction occurs on both single- and double-stranded DNA, and requires AlkB-bound non-heme Fe(2+), O(2) and alpha-ketogluterate to oxidize the offending methyl group. This is followed by the release of succinate, CO(2) and formaldehyde, and the restoration of undamaged A or C in DNA.
authors.affiliation: Biological Engineering Division and Center for Environmental Health Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Begley
authors.forename: Leona D
authors.initials: LD
authors.lastname: Samson
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D003596:Cytosine / Q000031:analogs & derivatives / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics; D019175:DNA Methylation; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000378:metabolism; D029968:Escherichia coli Proteins; D006899:Mixed Function Oxygenases; D010084:Oxidation-Reduction; D011485:Protein Binding
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; D003596:Cytosine; D006899:Mixed Function Oxygenases; C466427:AlkB protein, E coli; D000225:Adenine