SOLUTION CONFORMATION OF THE (+)-CIS-ANTI-[BP]DG ADDUCT IN A DNA DUPLEX - INTERCALATION OF THE COVALENTLY ATTACHED BENZO[A]PYRENYL RING INTO THE HELIX AND DISPLACEMENT OF THE MODIFIED DEOXYGUANOSINE
SOLUTION CONFORMATION OF THE (+)-CIS-ANTI-[BP]DG ADDUCT IN A DNA DUPLEX - INTERCALATION OF THE COVALENTLY ATTACHED BENZO[A]PYRENYL RING INTO THE HELIX AND DISPLACEMENT OF THE MODIFIED DEOXYGUANOSINE
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DOI：
10.1021/bi00067a001
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发表时间：
1993-04-27
期刊：
影响因子：
2.9
通讯作者：
PATEL, DJ
中科院分区：
文献类型：
--
作者：
COSMAN, M;DELOSSANTOS, C;PATEL, DJ
本文报道了位于DNA寡聚物双链体中C对侧的（+）-cis-anti-[BP]dG加合物的溶液结构，该DNA寡聚物双链体提供了第一个基于实验的多环芳烃与脱氧鸟苷的N2共价结合的嵌入复合物的溶液结构。对嵌入先前用立体异构反式加合物研究的互补11-mer双链体的相同d（C5-[BP]G6-C7）.d（G16-C17-G18）三核苷酸片段中的（+）-顺式-抗-[BP]dG加合物进行了组合核磁共振能量最小化计算研究。的苯并[a]芘基部分和核酸的可交换和不可交换的质子分配以下的二维NMR数据集在H2O和D2 O溶液中的分析。通过将由NOESY数据集推导的上限和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的约束，确定了（+）-顺式-反式-[BP]dG.dC 11-mer双链体的溶液结构。[BP] dG 6的苯并[a]芘环嵌入在右手DNA螺旋中完整的Watson-Crick dC5.dG18和dC7.dG16碱基对之间。苄基环位于小沟中，而芘基环与侧接的dC 5和dC 7碱基堆叠在同一条链上。[BP] dG 6的脱氧鸟苷环不是Watson-Crick碱基配对的，而是移位到小沟中，其平面平行于螺旋轴，并堆叠在dC 5的糖环上。配对链上的dC 17碱基通过插入的苯并[a]芘环从螺旋中心向大沟移位。（+）-顺式-抗-[BP]dG-dC 11-mer双链体的这种嵌入结构表现出几种异常位移的质子共振，这可以很容易地通过[BP] dG 6加合物的脱氧鸟苷和芘环的环电流贡献来解释。几个磷共振转移到低场和高场的未扰动的磷光谱区域，并已被分配到核苷酸间磷酸盐中心的[BP] dG 6的修改网站。这些研究定义了产生共价结合的（+）-顺式-抗-[BP]dG加合物的嵌入位点所需的中心三核苷酸片段处螺旋的变化。迄今为止，我们的结构研究允许将位于DNA螺旋中与dC相对的[BP]dG加合物分类为具有完整[BP]dG的位点II溶剂暴露结构。dC Watson-Crick配对，如对（+）-反式-抗-[BP]dG加合物所观察到的[Cosman等人，（1992）Proc.Natl. Acad. Sci. U.S.A. 89，1914-1918]和（-）-反式-抗-[BP]dG加合物[De洛斯桑托斯等人（1992）生物化学31，5245-5252]或位点I插入结构，其中[BP]dG和dC的脱氧鸟苷环被置换到相对的凹槽中，并且苯并[a]芘环插入到螺旋中，如对（+）-顺式-反-[BP] dG加合物。
This paper reports on the solution structure of the (+)-cis-anti-[BP]dG adduct positioned opposited C 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 stacks 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. Our structural studies to date permit the classification of [BP]dG adducts positioned opposite dC in DNA helices as either site II solvent-exposed structures with intact [BP]dG.dC Watson-Crick pairing as observed for the (+)-trans-anti-[BP]dG adduct [Cosman et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1914-1918] and (-)-trans-anti-[BP]dG adduct [De los Santos et al. (1992) Biochemistry 31, 5245-5252] or site I intercalative structures in which the deoxyguanosine ring of [BP]dG and dC are displaced into opposite grooves and the benzo[a]pyrene ring intercalates into the helix as observed for the (+)-cis-anti-[BP]dG adduct in this study.