Pardi A, Morden K M, Patel D J, Tinoco I
Biochemistry. 1983 Mar 1;22(5):1107-13. doi: 10.1021/bi00274a018.
The lifetimes for exchange of the imino protons in the dodecanucleotide d(C-G-C-G-A-A-T-T-C-G-C-G) upon binding of netropsin and/or actinomycin have been measured by proton nuclear magnetic resonance experiments. At high temperature these lifetimes were found to measure the lifetimes for opening of the base pairs in the double helix. Comparison of the opening rates in the dodecamer with those in the complex with netropsin (which binds at the -A-A-T-T- sequence) shows that there is not only a large kinetic stabilization of the A . T base pairs at the binding site but also a significant stabilization of the G . C base pairs adjacent to the netropsin binding site. For the complex with actinomycin, which intercalates at the G-C sites in the double strand, the lifetimes of the base pairs at the binding site increase upon binding of actinomycin, and the A . T base pairs in the central core are slightly kinetically destabilized by the actinomycin binding. The activation energies for exchange of the imino protons were also measured in the complexes and indicate that the mechanism for exchange of the imino protons is individual base-pair opening, where one base pair opens independently of the others. The effects of drug binding on the dynamics of individual base pairs in a double-stranded helix are discussed.
通过质子核磁共振实验，测量了在结合纺锤菌素和/或放线菌素时，十二聚体d（C-G-C-G-A-A-T-T-C-G-C-G）中亚氨基质子的交换寿命。在高温下，发现这些寿命可测量双螺旋中碱基对打开的寿命。将十二聚体中的打开速率与纺锤菌素复合物（在-A-A-T-T-序列处结合）中的打开速率进行比较，结果表明，不仅结合位点处的A·T碱基对有很大的动力学稳定性，而且与纺锤菌素结合位点相邻的G·C碱基对也有显著的稳定性。对于放线菌素复合物，它在双链中的G-C位点处插入，结合放线菌素后，结合位点处碱基对的寿命增加，而中心核心中的A·T碱基对因放线菌素结合而在动力学上略有不稳定。还测量了复合物中亚氨基质子交换的活化能，表明亚氨基质子交换的机制是单个碱基对打开，即一个碱基对独立于其他碱基对打开。讨论了药物结合对双链螺旋中单个碱基对动力学的影响。
