Zmijewski M J, Miller-Hatch K, Mikolajczak M
Chem Biol Interact. 1985 Jan;52(3):361-75. doi: 10.1016/0009-2797(85)90030-4.
The binding of naphthyridinomycin (NAP) to deoxyribonucleic acid was investigated using radioisotope labeled antibiotic. Dithiothreitol (DTT) enhances complex formation in a concentration dependent fashion but was found to be slightly inhibitory at concentrations above 10 mM. [C3H3]-NAP-DNA complexes, formed in the presence or absence of reducing reagents, were stable to Sephadex G-25 chromatography and precipitation with ethanol, indicating a strong bond formed between the drug and DNA. Time course studies showed that the difference between the binding of activated and non-activated antibiotic was a DTT-dependent burst. This was followed by a second phase of binding which was similar in both the activated and non-activated antibiotics. The activation of the antibiotic by DTT was a reversible reaction at pH 7.9. The activated form at pH 5.0 was extremely stable and did not revert to the unactivated form even after an 8-h incubation period. Antibiotic-DNA complex formation was pH independent between pH 5.0 and 7.0 for activated NAP. The non-activated antibiotic bound to DNA much better at pH 5.0 than at physiological pH values. Release of antibiotic from complexes (as followed by long term dialysis) formed in the presence of DTT and at pH 5.0 was biphasic, suggesting that the drug can bind to DNA in more than one way. A constant rate of antibiotic release was observed at pH 7.9 with or without DTT. At pH 2.0 and pH 12.0, greater than 95% of the antibiotic is released from the complexes. Most of the acid released antibiotic is NAP while most of the base released antibiotic had decomposed to a more polar compound. NAP binds well to calf thymus DNA, poly(dG) . poly(dC), and T4 DNA but shows significantly less affinity for poly(dA) . poly(dT), poly(dA . dT) . poly(dA . dT), poly(dG), poly(dC), poly(dI) . poly(dC) or poly(dG . dC) . poly(dG . dC). This specificity of NAP for DNA is similar to that observed for the pyrrolo(1,4)benzodiazepine antibiotics and saframycin A and S; all of which bind to double stranded DNA through their carbinolamine or masked carbinolamine functionalities. Two mechanisms which can explain the need for activation of NAP are also proposed.
使用放射性同位素标记的抗生素研究了萘啶霉素（NAP）与脱氧核糖核酸的结合。二硫苏糖醇（DTT）以浓度依赖的方式增强复合物的形成，但发现在浓度高于10 mM时具有轻微的抑制作用。在存在或不存在还原剂的情况下形成的[C3H3]-NAP-DNA复合物对Sephadex G-25色谱和乙醇沉淀稳定，表明药物与DNA之间形成了强键。时间进程研究表明，活化抗生素与未活化抗生素结合的差异是一个依赖于DTT的快速反应阶段。随后是第二个结合阶段，在活化和未活化的抗生素中都相似。DTT对抗生素的活化在pH 7.9时是一个可逆反应。在pH 5.0时的活化形式极其稳定，即使经过8小时的孵育期也不会恢复到未活化形式。对于活化的NAP，抗生素-DNA复合物的形成在pH 5.0至7.0之间与pH无关。未活化的抗生素在pH 5.0时比在生理pH值下与DNA结合得更好。在存在DTT且pH 5.0的情况下形成的复合物中抗生素的释放（通过长期透析监测）是双相的，表明药物可以以多种方式与DNA结合。在有或没有DTT的情况下，在pH 7.9时观察到抗生素的恒定释放速率。在pH 2.0和pH 12.0时，超过95%的抗生素从复合物中释放出来。酸性条件下释放的大部分抗生素是NAP，而碱性条件下释放的大部分抗生素已分解为极性更强的化合物。NAP与小牛胸腺DNA、聚（dG）·聚（dC）和T4 DNA结合良好，但对聚（dA）·聚（dT）、聚（dA·dT）·聚（dA·dT）、聚（dG）、聚（dC）、聚（dI）·聚（dC）或聚（dG·dC）·聚（dG·dC）的亲和力明显较低。NAP对DNA的这种特异性与观察到的吡咯并（1,4）苯并二氮杂卓类抗生素以及沙弗拉霉素A和S相似；所有这些抗生素都通过它们的甲醇胺或掩蔽的甲醇胺官能团与双链DNA结合。还提出了两种可以解释NAP活化需求的机制。
