Nakano Shu-Ichi, Watabe Takaaki, Sugimoto Naoki
Department of Nanobiochemistry, Faculty of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, 7-1-20, Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
Department of Chemistry, Faculty of Science and Engineering, Konan University, 8-9-1, Okamoto, Higashinada-ku, Kobe, 658-8501, Japan.
Chemphyschem. 2017 Dec 15;18(24):3614-3619. doi: 10.1002/cphc.201700882. Epub 2017 Nov 2.
Nucleic acid enzymes require specific metal ions to be catalytically active. The functions of the metal ions having structural and catalytic roles are affected by competing cations. Large-sized tetraalkylammonium ions have a propensity to preferentially bind to single strands of RNA and DNA. Here, the large cations are used in the reactions of lead-dependent ribozyme and 17E deoxyribozyme that require divalent metal ions to cleave a nucleic acid substrate. Kinetic analysis shows that tetraalkylammonium ions influence the rate of substrate cleavage, and the effects are different depending on the nucleic acid enzymes and metal ions used. Importantly, the large cations used here increase the dependence of cleavage rates on metal ion concentration and enhance the ability of the enzyme to monitor changes in metal ion concentrations. The same effect is also observed for the metal ion concentration dependence of the thermal stability of RNA and DNA structures, indicating that the large cations affect the binding of structural metal ions. The use of large tetraalkylammonium ions provides new ways to study the importance of metal ions to nucleic acid enzymes, and also to modulate the functionality of nucleic acid enzymes.
核酸酶需要特定的金属离子才能具有催化活性。具有结构和催化作用的金属离子的功能会受到竞争性阳离子的影响。大尺寸的四烷基铵离子倾向于优先结合RNA和DNA的单链。在此，大阳离子被用于依赖铅的核酶和17E脱氧核酶的反应中，这两种酶需要二价金属离子来切割核酸底物。动力学分析表明，四烷基铵离子会影响底物切割速率，并且根据所使用的核酸酶和金属离子的不同，影响也有所不同。重要的是，此处使用的大阳离子增加了切割速率对金属离子浓度的依赖性，并增强了酶监测金属离子浓度变化的能力。对于RNA和DNA结构热稳定性的金属离子浓度依赖性，也观察到了相同的效应，这表明大阳离子会影响结构金属离子的结合。使用大尺寸的四烷基铵离子为研究金属离子对核酸酶的重要性提供了新方法，同时也为调节核酸酶的功能提供了新途径。
