Aich P, Dasgupta D
Crystallography & Molecular Biology Division, Saha Institute of Nuclear Physics, Calcutta, India.
Biochem Biophys Res Commun. 1990 Dec 14;173(2):689-96. doi: 10.1016/s0006-291x(05)80090-7.
Mithramycin(MTR, structure shown in Figure 1) [and the related compound Chromomycin A3(CHRA3)] are antitumor antibiotics which inhibit DNA dependent RNA polymerase activity via reversible interaction with DNA only in the presence of divalent metal ion such as Mg++. In order to understand the role of Mg++ in MTR-DNA interaction, absorbance and CD spectroscopic techniques are employed to study the binding of MTR to Mg++. These studies show: i) the drug alone binds to Mg++ and ii) two different types of drug-Mg++ complexes are formed at low(Complex I) and high(Complex II) ratios of the concentration of Mg++ and MTR. We propose that these two complexes would bind to the same DNA with different affinities and rates. This result suggests that the relative concentration of Mg++ is an important factor to be taken into account to understand the molecular basis of MTR-DNA interaction.
光神霉素（MTR，结构见图1）[以及相关化合物色霉素A3（CHRA3）]是抗肿瘤抗生素，仅在二价金属离子如Mg++存在的情况下，通过与DNA的可逆相互作用抑制依赖DNA的RNA聚合酶活性。为了了解Mg++在MTR与DNA相互作用中的作用，采用吸光度和圆二色光谱技术研究MTR与Mg++的结合。这些研究表明：i）药物单独与Mg++结合；ii）在Mg++和MTR浓度的低（复合物I）和高（复合物II）比例下形成两种不同类型的药物-Mg++复合物。我们认为这两种复合物将以不同的亲和力和速率与相同的DNA结合。这一结果表明，Mg++的相对浓度是理解MTR与DNA相互作用分子基础时需要考虑的一个重要因素。
