Fulmer P, Zhao C, Li W, DeRose E, Antholine W E, Petering D H
Department of Chemistry, University of Wisconsin-Milwaukee, 53211, USA.
Biochemistry. 1997 Apr 8;36(14):4367-74. doi: 10.1021/bi9625354.
Co- and Fe-bleomycins (Blms) have been reacted with DNAa, d(GGAAGCTTCC)2, containing a specific site for cleavage, and DNAb, d(GGAAATTTCC)2, a closely related nonspecific 10-mer, to survey whether features of structure and reactivity of these adducts vary systematically as a function of the base sequence of the DNA oligomer. The ESR spectrum of NO-Fe(II)BlmDNAa is rhombically perturbed in comparison with that of NO-Fe(II)BlmDNAb, which is nearly identical to the spectrum of NO-Fe(II)Blm. The ESR spectrum of Fe(III)BlmDNAa in phosphate buffer is low-spin; that of Fe(III)BlmDNAb is high-spin as seen with Fe(III)Blm alone. According to absorbance spectroscopy, O2-Fe(II)BlmDNAa is stabilized in comparison with the DNAb adduct. Similar stabilization of O2-Co(II)Blm bound to DNAa but not to DNAb was also observed by ESR spectroscopy. HO2(-)-Co(III)Blm A2 binds in slow exchange on the NMR time scale to DNAa at its 5'-G-pyrimidine-3' site of cleavage. In contrast, fluorescence and NMR spectroscopy demonstrate that most of HO2(-)-Co(III)Blm A2 binds stoichiometrically in fast exchange to DNAb. The reactions of Fe(III)BlmDNAa and Fe(III)BlmDNAb with ascorbate and O2 reveal that the latter becomes activated and cleaves its 10-mer, producing base propenals, at a faster initial rate. Thus, in two series of metallobleomycins, (A) NO-Fe(II)Blm, O2-Fe(II)Blm, Fe(III)Blm in phosphate buffer, and HO2(-)-Fe(III)Blm and (B) O2-Co(II)Blm and HO2(-)-Co(III)Blm, the metal domain of each species interacts differently with DNA depending upon its base sequence.
将钴博来霉素（Blm）和铁博来霉素与含有特定切割位点的DNAa（d(GGAAGCTTCC)2）以及与之密切相关的非特异性10聚体DNAb（d(GGAAATTTCC)2）反应，以研究这些加合物的结构和反应性特征是否会随着DNA寡聚物碱基序列的变化而系统地改变。与NO-Fe(II)BlmDNAb的电子顺磁共振（ESR）谱相比，NO-Fe(II)BlmDNAa的ESR谱呈菱形扰动，而NO-Fe(II)BlmDNAb的ESR谱与NO-Fe(II)Blm的谱几乎相同。在磷酸盐缓冲液中，Fe(III)BlmDNAa的ESR谱为低自旋；Fe(III)BlmDNAb的ESR谱为高自旋，与单独的Fe(III)Blm情况相同。根据吸光光谱法，与DNAb加合物相比，O2-Fe(II)BlmDNAa更稳定。通过ESR光谱法也观察到，与DNAa结合的O2-Co(II)Blm具有类似的稳定性，但与DNAb结合时则不然。HO2(-)-Co(III)Blm A2在核磁共振（NMR）时间尺度上以缓慢交换的方式在其切割位点的5'-G-嘧啶-3'处与DNAa结合。相比之下，荧光光谱法和NMR光谱法表明，大多数HO2(-)-Co(III)Blm A2以化学计量比在快速交换的情况下与DNAb结合。Fe(III)BlmDNAa和Fe(III)BlmDNAb与抗坏血酸和O2的反应表明，后者被激活并以更快的初始速率切割其10聚体，产生碱基丙烯醛。因此，在两组金属博来霉素中，（A）NO-Fe(II)Blm、O2-Fe(II)Blm、磷酸盐缓冲液中的Fe(III)Blm以及HO2(-)-Fe(III)Blm和（B）O2-Co(II)Blm和HO2(-)-Co(III)Blm，每个物种的金属结构域根据其碱基序列与DNA的相互作用方式不同。
