Hoehn S T, Turner C J, Stubbe J
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Nucleic Acids Res. 2001 Aug 15;29(16):3413-23. doi: 10.1093/nar/29.16.3413.
The antitumor antibiotic bleomycin causes two major lesions in the deoxyribose backbone of DNA: formation of 4'-keto abasic sites and formation of strand breaks with 3'-phosphoglycolate and 5'-phosphate ends. As a model for the 4'-keto abasic site, we have characterized an abasic site (X) in d(CCAAAGXACTGGG).d(CCCAGTACTTTGG) by two-dimensional NMR spectroscopy. A total of 475 NOEs and 101 dihedral angles provided the restraints for molecular modeling. Four unusual NOEs were observed between each anomer of the abasic site and the neighboring bases. In addition, four coupling constants for adjacent protons of the deoxyribose of both the alpha and beta anomers of the abasic site were observed. The modeling suggests that for both anomers the abasic site is extrahelical, without significant distortion of the backbone opposite the lesion. The coupling constants further allowed assignment of an unusual sugar pucker for each anomer. The unique position of the abasic site in our structural model for each anomer is discussed in terms of repair of such lesions in vivo.
抗肿瘤抗生素博来霉素会在DNA的脱氧核糖主链上造成两种主要损伤:4'-酮基无碱基位点的形成以及带有3'-磷酸乙醇酸和5'-磷酸末端的链断裂。作为4'-酮基无碱基位点的模型,我们通过二维核磁共振光谱对d(CCAAAGXACTGGG).d(CCCAGTACTTTGG)中的一个无碱基位点(X)进行了表征。总共475个核Overhauser效应(NOE)和101个二面角为分子建模提供了限制条件。在无碱基位点的每个异头物与相邻碱基之间观察到四个异常的NOE。此外,还观察到了无碱基位点的α和β异头物的脱氧核糖相邻质子的四个耦合常数。建模表明,对于两种异头物,无碱基位点都是螺旋外的,在损伤相对的主链处没有明显扭曲。耦合常数进一步允许为每个异头物指定一种不寻常的糖环构象。我们根据体内此类损伤的修复情况讨论了无碱基位点在每个异头物结构模型中的独特位置。