Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, NY 10065, USA; Department of Life Science, College of Science & General Studies, Alfaisal University, Riyadh, Saudi Arabia.
Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, NY 10065, USA.
Int J Biol Macromol. 2019 Jan;121:947-955. doi: 10.1016/j.ijbiomac.2018.10.135. Epub 2018 Oct 18.
Viral protein linked to the genome (VPg) of turnip mosaic virus (TuMV) interacts with eIF4F and plays an important role in cap-independent initiation of protein synthesis. In order to understand the importance of PABP on the interaction of eIF4F with VPg, we report that PABP enhanced the binding affinity ~3- and 4-fold for eIF4F-VPg and eIF4F·eIF4B-VPg, respectively. PABP enhances rates of protein synthesis in uncapped viral mRNA and correlates with binding affinity of eIF4F with VPg. Temperature dependent (278 K to 298 K) showed ~3-fold increase in eIF4F binding to VPg in presence of PABP and eIF4B. A van't Hoff analysis reveals that eIF4F·eIF4B·PABP binding to VPg was enthalpy-driven and entropy-favorable with 30% increase in enthalpic contribution and 81% decrease in entropic contribution. PABP increased the association rate (4-fold) and decreased the dissociation rate (3-fold) for the eIF4F·eIF4B binding to VPg. PABP significantly decreased the activation energy of eIF4F·eIF4B binding to VPg. When both PABP and eIF4B were present, not only was the energy barrier reduced but the binding rate was faster and dissociation rate was slower for the protein-protein complex formation. These results suggest increased hydrogen bonding and an overall conformational change, and more stable platform for effective viral translation.
芜菁花叶病毒（TuMV）基因组相关的病毒蛋白（VPg）与 eIF4F 相互作用，在依赖 cap 的蛋白合成起始中发挥重要作用。为了了解 PABP 在 eIF4F 与 VPg 相互作用中的重要性，我们报告 PABP 分别增强了 eIF4F-VPg 和 eIF4F·eIF4B-VPg 的结合亲和力约 3 倍和 4 倍。PABP 增强了无帽病毒 mRNA 的蛋白合成速率，并与 eIF4F 与 VPg 的结合亲和力相关。变温（278 K 至 298 K）显示在 PABP 和 eIF4B 存在下 eIF4F 与 VPg 的结合增加了约 3 倍。范特霍夫分析表明，eIF4F·eIF4B·PABP 与 VPg 的结合是焓驱动和熵有利的，焓贡献增加 30%，熵贡献减少 81%。PABP 增加了 eIF4F·eIF4B 与 VPg 的结合速率（4 倍），降低了解离速率（3 倍）。PABP 显著降低了 eIF4F·eIF4B 与 VPg 结合的活化能。当同时存在 PABP 和 eIF4B 时，不仅降低了能量势垒，而且蛋白质-蛋白质复合物的形成速度更快，解离速度更慢。这些结果表明氢键增加和整体构象变化，以及更稳定的有效病毒翻译平台。
