Cosman M, de los Santos C, Fiala R, Hingerty B E, Ibanez V, Luna E, Harvey R, Geacintov N E, Broyde S, Patel D J
Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Biochemistry. 1993 Apr 27;32(16):4145-55. doi: 10.1021/bi00067a001.
This paper reports on the solution structure of the (+)-cis-anti-[BP]dG adduct positioned opposite dC in a DNA oligomer duplex which provides the first experimentally based solution structure of an intercalative complex of a polycyclic aromatic hydrocarbon covalently bound to the N2 of deoxyguanosine. The combined NMR-energy minimization computation studies were undertaken on the (+)-cis-anti-[BP]dG adduct embedded in the same d(C5-[BP]G6-C7).d(G16-C17-G18) trinucleotide segment of the complementary 11-mer duplex studied previously with the stereoisomeric trans adducts. The exchangeable and nonexchangeable protons of the benzo[a]pyrenyl moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution structure of the (+)-cis-anti-[BP]dG-dC 11-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by upper and lower bounds deduced from NOESY data sets as restraints in energy minimization computations. The benzo[a]pyrene ring of [BP]dG6 is intercalated between intact Watson-Crick dC5.dG18 and dC7.dG16 base pairs in a right-handed DNA helix. The benzylic ring is in the minor groove while the pyrenyl ring sacks with flanking dC5 and dC7 bases on the same strand. The deoxyguanosine ring of [BP]dG6 is not Watson-Crick base paired but displaced into the minor groove with its plane parallel to the helix axis and stacks over the sugar ring of dC5. The dC17 base on the partner strand is displaced from the center of the helix toward the major groove by the intercalated benzo[a]pyrene ring. This intercalative structure of the (+)-cis-anti-[BP]dG-dC 11-mer duplex exhibits several unusually shifted proton resonances which can be readily accounted for by the ring current contributions of the deoxyguanosine and pyrenyl rings of the [BP]dG6 adduct. Several phosphorus resonances are shifted to low and high field of the unperturbed phosphorus spectral region and have been assigned to internucleotide phosphates centered about the [BP]dG6 modification site. These studies define the changes in the helix at the central trinucleotide segment needed to generate the intercalation site for the covalently bound (+)-cis-anti-[BP]dG adduct.(ABSTRACT TRUNCATED AT 400 WORDS)
本文报道了位于DNA寡聚物双链体中与dC相对的(+)-顺式-反式-[BP]dG加合物的溶液结构，该结构提供了多环芳烃与脱氧鸟苷N2共价结合的嵌入复合物的首个基于实验的溶液结构。对嵌入先前研究的具有立体异构反式加合物的互补11聚体双链体相同d(C5-[BP]G6-C7).d(G16-C17-G18)三核苷酸片段中的(+)-顺式-反式-[BP]dG加合物进行了NMR-能量最小化联合计算研究。在H2O和D2O溶液中分析二维NMR数据集后，确定了苯并[a]芘部分和核酸的可交换和不可交换质子。通过将由NOESY数据集推导的上下限定义的分子内和分子间质子-质子距离作为能量最小化计算中的约束条件，确定了(+)-顺式-反式-[BP]dG-dC 11聚体双链体的溶液结构。[BP]dG6的苯并[a]芘环插入右手DNA螺旋中完整的沃森-克里克dC5.dG18和dC7.dG16碱基对之间。苄基环位于小沟中，而芘基环与同一条链上的侧翼dC5和dC7碱基堆积。[BP]dG6的脱氧鸟苷环不是沃森-克里克碱基对，而是位移到小沟中，其平面与螺旋轴平行，并堆积在dC5的糖环上。互补链上的dC17碱基因嵌入的苯并[a]芘环而从螺旋中心向大沟位移。(+)-顺式-反式-[BP]dG-dC 11聚体双链体的这种嵌入结构表现出几个异常位移的质子共振，这可以很容易地由[BP]dG加合物的脱氧鸟苷环和芘基环的环流贡献来解释。几个磷共振位移到未受干扰的磷光谱区域的低场和高场，并已被指定为以[BP]dG6修饰位点为中心的核苷酸间磷酸酯。这些研究确定了在中央三核苷酸片段处螺旋的变化，以产生共价结合的(+)-顺式-反式-[BP]dG加合物的嵌入位点。(摘要截于400字)
