Ruszczynska Katarzyna, Kamienska-Trela Krystyna, Wojcik Jacek, Stepinski Janusz, Darzynkiewicz Edward, Stolarski Ryszard
Department of Biophysics, Institute of Experimental Physics, Warsaw University, Warsaw, Poland.
Biophys J. 2003 Sep;85(3):1450-6. doi: 10.1016/S0006-3495(03)74577-9.
Electric charge distribution in mRNA 5' cap terminus has been exhaustively characterized in respect to the affinity for cap-binding proteins. Formation of the stacked configuration of positively charged 7-methylguanine in between two aromatic amino acid rings, known as sandwich cation-pi stacking, is thought to be prerequisite for the specific recognition of the cap by eukaryotic initiation factor eIF4E; i.e., discrimination between the cap and nucleotides without the methyl group at N(7). Nuclear magnetic resonance spectroscopy of (15)N/(13)C-double-labeled 7-methylguanosine 5'-triphosphate and 7-methylguanosine, as well as their unsubstituted counterparts, GTP and guanosine, yielded characteristic changes of the electron-mediated spin-spin couplings and chemical shifts due to the methylation at N(7). The experimentally measured changes of the nuclear magnetic resonance parameters have been analyzed in respect to the electric charge distribution calculated by means of quantum chemical methods, and interpreted in terms of new proposed positive charge localization in the 7-methylguanine five-member ring.
就与帽结合蛋白的亲和力而言，mRNA 5' 帽末端的电荷分布已得到详尽表征。两个芳香族氨基酸环之间带正电荷的 7-甲基鸟嘌呤形成堆叠构型，即所谓的夹心阳离子-π堆积，被认为是真核起始因子 eIF4E 特异性识别帽的先决条件；也就是说，区分帽与 N(7) 处没有甲基的核苷酸。对 (15)N/(13)C 双标记的 7-甲基鸟苷 5'-三磷酸和 7-甲基鸟苷及其未取代的对应物 GTP 和鸟苷进行核磁共振光谱分析，结果显示由于 N(7) 处的甲基化，电子介导的自旋-自旋耦合和化学位移发生了特征性变化。已根据通过量子化学方法计算的电荷分布对实验测量的核磁共振参数变化进行了分析，并根据新提出的 7-甲基鸟嘌呤五元环中的正电荷定位进行了解释。
