Tomasz M, Chowdary D, Lipman R, Shimotakahara S, Veiro D, Walker V, Verdine G L
Proc Natl Acad Sci U S A. 1986 Sep;83(18):6702-6. doi: 10.1073/pnas.83.18.6702.
The antitumor antibiotic mitomycin C is shown to form a covalent complex with calf thymus DNA under anaerobic conditions in the presence of either NADPH cytochrome c reductase/NADPH, xanthine oxidase/NADH, or the chemical reducing system H2/PtO2. Digestion of the complex with DNase I/snake venom diesterase/alkaline phosphatase yields a single mitomycin deoxyguanosine adduct as the major DNA alkylation product, identified as N2-(2'' beta,7''-diaminomitosen-1'' alpha-yl) 2'-deoxyguanosine (Structure 2). Two minor adducts, 2-5% each of the total adduct pool, are isolated and identified as the 1'' beta stereoisomer of 2 (Structure 3), and 10''-decarbamoyl-2 (Structure 7). The same results were obtained with M13 DNA and poly(dG-dC).poly(dG-dC); however, in the latter case, a minor adduct apparently possessing two deoxyguanosine and one mitomycin unit is isolated. Digestion of the covalent mitomycin-calf thymus DNA complex with nuclease P1 yields four dinucleotide adducts, all of which consist of 2 linked at its 3' end to each of the four possible 5' nucleotides (A, T, G, and C). Upon treatment of each dinucleotide adduct with snake venom diesterase/alkaline phosphatase, 2 is released along with the corresponding free nucleoside. In apparent conflict with the present results, previous reports from another laboratory have indicated that modification of calf thymus DNA by mitomycin C under conditions identical to those described here result in the isolation of three mitomycin C mononucleotide adducts possessing linkages of the drug to N2 and O6 of guanine and N6 of adenine. Evidence is shown suggesting that the latter adducts are actually three of the above four dinucleotide derivatives of 2 obtained independently by us and, thus, all of them in fact possess an identical N2-mitosenylguanine adduct moiety. Model-building studies indicate an excellent fit of the guanine N2-linked drug molecule inside the minor groove of B-DNA with no appreciable distortion of the DNA structure.
抗肿瘤抗生素丝裂霉素C在厌氧条件下，于烟酰胺腺嘌呤二核苷酸磷酸细胞色素c还原酶/烟酰胺腺嘌呤二核苷酸磷酸、黄嘌呤氧化酶/烟酰胺腺嘌呤二核苷酸或化学还原体系氢气/二氧化铂存在时，可与小牛胸腺DNA形成共价复合物。用脱氧核糖核酸酶I/蛇毒磷酸二酯酶/碱性磷酸酶消化该复合物，产生一种单一的丝裂霉素脱氧鸟苷加合物作为主要的DNA烷基化产物，鉴定为N2-(2''β,7''-二氨基丝裂霉素-1''α-基)2'-脱氧鸟苷（结构2）。分离出两种次要加合物，各占总加合物池的2 - 5%，鉴定为2的1''β立体异构体（结构3）和10''-脱氨甲酰基-2（结构7）。用M13 DNA和聚(dG-dC).聚(dG-dC)也得到相同结果；然而，在后一种情况下，分离出一种明显含有两个脱氧鸟苷和一个丝裂霉素单元的次要加合物。用核酸酶P1消化共价的丝裂霉素-小牛胸腺DNA复合物，产生四种二核苷酸加合物，所有这些加合物均由2在其3'端与四种可能的5'核苷酸（腺嘌呤、胸腺嘧啶、鸟嘌呤和胞嘧啶）中的每一种相连组成。用蛇毒磷酸二酯酶/碱性磷酸酶处理每种二核苷酸加合物后，会释放出2以及相应的游离核苷。与目前的结果明显矛盾的是，另一个实验室先前的报告表明，在与本文所述相同的条件下，丝裂霉素C对小牛胸腺DNA的修饰导致分离出三种丝裂霉素C单核苷酸加合物，药物与鸟嘌呤的N2和O6以及腺嘌呤的N6相连。有证据表明，后一种加合物实际上是我们独立获得的上述2的四种二核苷酸衍生物中的三种，因此，它们实际上都具有相同的N2-丝裂霉素基鸟嘌呤加合物部分。模型构建研究表明，鸟嘌呤N2连接的药物分子在B-DNA小沟内拟合良好，DNA结构无明显扭曲。
