1eh8
BENZYLATED HUMAN O6-ALKYLGUANINE-DNA ALKYLTRANSFERASE
Structural highlights
FunctionMGMT_HUMAN Involved in the cellular defense against the biological effects of O6-methylguanine (O6-MeG) in DNA. Repairs alkylated guanine in DNA by stoichiometrically transferring the alkyl group at the O-6 position to a cysteine residue in the enzyme. This is a suicide reaction: the enzyme is irreversibly inactivated. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedHuman O(6)-alkylguanine-DNA alkyltransferase (AGT), which directly reverses endogenous alkylation at the O(6)-position of guanine, confers resistance to alkylation chemotherapies and is therefore an active anticancer drug target. Crystal structures of active human AGT and its biologically and therapeutically relevant methylated and benzylated product complexes reveal an unexpected zinc-stabilized helical bridge joining a two-domain alpha/beta structure. An asparagine hinge couples the active site motif to a helix-turn-helix (HTH) motif implicated in DNA binding. The reactive cysteine environment, its position within a groove adjacent to the alkyl-binding cavity and mutational analyses characterize DNA-damage recognition and inhibitor specificity, support a structure-based dealkylation mechanism and suggest a molecular basis for destabilization of the alkylated protein. These results support damaged nucleotide flipping facilitated by an arginine finger within the HTH motif to stabilize the extrahelical O(6)-alkylguanine without the protein conformational change originally proposed from the empty Ada structure. Cysteine alkylation sterically shifts the HTH recognition helix to evidently mechanistically couple release of repaired DNA to an opening of the protein fold to promote the biological turnover of the alkylated protein. Active and alkylated human AGT structures: a novel zinc site, inhibitor and extrahelical base binding.,Daniels DS, Mol CD, Arvai AS, Kanugula S, Pegg AE, Tainer JA EMBO J. 2000 Apr 3;19(7):1719-30. PMID:10747039[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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