1jo1
N7-Guanine Adduct of 2,7-diaminomitosene with DNA
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OverviewOverview
2,7-Diaminomitosene (2,7-DAM), the major metabolite of the antitumor, antibiotic mitomycin C, forms DNA adducts in tumor cells. 2,7-DAM was, reacted with the deoxyoligonucleotide d(GTGGTATACCAC) under reductive, alkylation conditions. The resulting DNA adduct was characterized as, d(G-T-G-[M]G-T-A-T-A-C-C-A-C) (5), where [M]G stands for a covalently, modified guanine, linked at its N7-position to C10 of the mitosene. The, adducted oligonucleotide complements with itself, retaining 2-fold, symmetry in the 2:1 drug-duplex complex, and provides well-resolved NMR, spectra, amenable for structure determination. Adduction at the, N7-position of G4 ([M]G, 4) is characterized by a downfield shift of the, G4(H8) proton and separate resonances for G4(NH(2)) protons. We assigned, the exchangeable and nonexchangeable proton resonances of the mitosene and, the deoxyoligonucleotide in adduct duplex 5 and identified intermolecular, proton-proton NOEs necessary for structural characterization. Molecular, dynamics computations guided by 126 intramolecular and 48 intermolecular, distance restraints were performed to define the solution structure of the, 2,7-DAM-DNA complex 5. A total of 12 structures were computed which, exhibited pairwise rmsd values in the 0.54-1.42 A range. The 2,7-DAM, molecule is anchored in the major groove of DNA by its C10 covalently, linked to G4(N7) and is oriented 3' to the adducted guanine. The presence, of 2,7-DAM in the major groove does not alter the overall B-DNA helical, structure. Alignment in the major groove is a novel feature of the, complexation of 2,7-DAM with DNA; other known major groove alkylators such, as aflatoxin, possessing aromatic structural elements, form intercalated, complexes. Thermal stability properties of the 2,7-DAM-DNA complex 5 were, characteristic of nonintercalating guanine-N7 alkylating agents. Marked, sequence selectivity of the alkylation by 2,7-DAM was observed, using a, series of oligonucleotides incorporating variations of the 5'-TGGN, sequence as substrates. The selectivity correlated with the sequence, specificity of the negative molecular electrostatic potential of the major, groove, suggesting that the alkylation selectivity of 2,7-DAM is, determined by sequence-specific variation of the reactivity of the DNA., The unusual, major groove-aligned structure of the adduct 5 may account, for the low cytotoxicity of 2,7-DAM.
About this StructureAbout this Structure
1JO1 is a Protein complex structure of sequences from [1] with DAJ as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Solution structure of a guanine-N7-linked complex of the mitomycin C metabolite 2,7-diaminomitosene and DNA. Basis of sequence selectivity., Subramaniam G, Paz MM, Suresh Kumar G, Das A, Palom Y, Clement CC, Patel DJ, Tomasz M, Biochemistry. 2001 Sep 4;40(35):10473-84. PMID:11523988
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