Lee M, Pon R T, Krowicki K, Lown J W
Department of Chemistry, University of Alberta, Edmonton, Canada.
J Biomol Struct Dyn. 1988 Feb;5(4):939-49. doi: 10.1080/07391102.1988.10506436.
High field 1H-NMR techniques have been used to examine the sequence dependent binding of a lexitropsin, the bis-imidazole analogue of netropsin 1, to the decadeoxyribonucleotide d-[CGCAATTGCG]2. The non-exchangeable and imino protons of the 1:1 lexitropsin:DNA complex are assigned by 1D-NOE difference and COSY methods. Addition of 1 to the DNA resulted in marked drug induced chemical shift changes of both the non-exchangeable and imino protons of A(4,5) and T(6,7). These results suggest that the lexitropsin is located in the minor groove along A(4) to T(7) of the DNA. Weaker chemical shift changes are observed for C(3) and G(8) which suggest that the bisimidazole moiety of 1 can also accept G.C sites. Specific NOEs seen between the lexitropsin (H2, H14 and H15) and DNA (AH2(4) and AH2(5] confirmed that the N to C-terminii of 1 is, on average, bound centrally to the sequence in the direction 5'-AATT-3'. However, netropsin 2 is shown to bind tightly only to the AATT sequence. Exchange NMR effects permit the estimate of the rate of exchange of the lexitropsin 1 between the two equivalent sites on the DNA to be approximately 160s and 24s for netropsin under comparable conditions. Several factors contributing to the sequence specificity of lexitropsin binding are discussed.
高场¹H-NMR技术已被用于研究一种偏位菌素（奈替米星1的双咪唑类似物）与十脱氧核糖核苷酸d-[CGCAATTGCG]₂的序列依赖性结合。通过一维NOE差异和COSY方法确定了1:1偏位菌素:DNA复合物中不可交换质子和亚氨基质子的归属。向DNA中加入1会导致A(4,5)和T(6,7)的不可交换质子和亚氨基质子出现明显的药物诱导化学位移变化。这些结果表明偏位菌素位于DNA从A(4)到T(7)的小沟中。在C(3)和G(8)处观察到较弱的化学位移变化，这表明1的双咪唑部分也可以与G.C位点结合。在偏位菌素（H2、H14和H15）与DNA（AH2(4)和AH2(5)）之间观察到的特定NOE证实，1的N端到C端平均在5'-AATT-3'方向上与该序列的中心结合。然而，奈替米星2仅紧密结合于AATT序列。交换NMR效应使得在可比条件下，偏位菌素1在DNA上两个等效位点之间的交换速率估计约为160s，奈替米星的交换速率为24s。讨论了导致偏位菌素结合序列特异性产生的几个因素。
