NMR STUDIES OF CO BLEOMYCIN & DNA COMPLEXES

共-博莱霉素(CoBLM)A2绿的溶液结构 过氧化氢(OJ-CoBLM)与自互补络合物 在C6具有切割位点的寡核苷酸d(CCAGQCCTGG)已经被 用二维核磁共振波谱方法和分子动力学确定 计算。分子间NOEE(介于CoBLm A2 Green和DNA之间) 和分子内NO(CoBLMA2绿色内的61个)定义了 CoBLMA2绿色相对于其单分子的位置和方向 双链中的结合位点。这些研究提供了第一个 双噻唑尾部成键方式的结构洞察 CoBLMA2对DNA的绿色作用是其切割的特异性基础 D(G-Py)序列中的嘧啶(Py)及其定向 过氧化氢相对于4‘碳的末端氧 DNA中的氢键正在断裂。4-氨基和N3 CoBLMA2中的嘧啶环形成专性氢键 分别与G5的N3和2-氨基在 并提供了一个不同寻常的小凹槽底座的例子 三重类相互作用。偏爱G而不偏爱A的基础，5‘ 到Py裂解位点，这样就建立了。最引人注目的 这种结构的特征是观察到与质子相关联的 CoBLMA2绿的过氧化氢作用及其观察 分子间对C6和C7的小槽质子的影响 双面打印。因此，这种结构提供了一种罕见的类似于 一种准备引发氢原子的反应性中间体 抽象事件。分子模拟揭示了泰国的远端 过氧化氢的氧是C6的4‘-氢的2.5A。一个 分子间额外的分子内氢键数目 还提出了过氧化氢配体和多肽连接区， 它们似乎在定位被动型 在被提取的氢原子附近的中间体。这一结构 模型做出了许多预测，这些预测可以在实验中得到验证。

The solution structure of Co-Bleomycin (CoBLM) A2 green (the hydroperoxide form oj CoBLM) complexed with self-complementary oligonucleotide d(CCAGQCCTGG) with a cleavage site at C6 has been determined by 2D NMR spectroscopic methods and molecular dynamics calculations. Intermolecular NOEe (60 between CoBLM A2 green and DNA) and intrarnolecular NOEs (61 within CoBLM A2 green) have defined the position and orientation of CoBLM A2 green with respect to its single binding site in the duplex. These studies have provided the first structural insight into the mode of bonding of the bithiazole tail of CoBLM A2 green to DNA, the basis for specificity of its cleavage ai pyrimidines (Py) in d(G-Py) sequences, and the orientation of its terminal oxygen of the hydroperoxide relative to the 4' carbon hydrogen bond being cleaved in the DNA. The 4-amino group and the N3 of the pyrimidine ring of CoBLM A2 green form specific hydrogen bonds with the N3 and the 2-amino group, respectively, of the G5 in the duplex and provide an unusual example of a minor groove base triple-like interaction. A basis for the preference for G over A, 5' to the Py cleavage site, is thus established. The most remarkable feature of this structure is the observation of the proton associated with the hydroperoxide of CoBLM A2 green and its observed intermolecular NOEs to the minor groove protons of C6 and C7 of the duplex. Thus, this structure provides a rare snapshot of an analog of a reactive intermediate poised to initiate the hydrogen atom abstraction event. The molecular modeling reveals thai the distal oxygen of the hydroperoxide is 2.5 A from the 4'-hydrogen of C6. A number of additional intramolecular hydrogen bonds between the hydroperoxide ligand and the peptide linker region are also proposed, which appear to play a key role in positioning the reactive intermediate near the hydrogen atom being abstracted. This structural model makes a number of predictions that can be tested experimentally.