Li Yang, Zhang Yuwei, Großerüschkamp Frederik, Stephan Sara, Cui Qiang, Kötting Carsten, Xia Fei, Gerwert Klaus
School of Chemistry and Molecular Engineering , East China Normal University , Shanghai 200062 , China.
School of Information Science and Engineering , Shandong Agricultural University , Taian 271018 , China.
J Phys Chem Lett. 2018 Mar 15;9(6):1312-1317. doi: 10.1021/acs.jpclett.8b00342. Epub 2018 Mar 2.
The oncogenic Ras protein adopts various specific conformational states to execute its function in signal transduction. The large number of Ras structures obtained from X-ray and NMR experiments illustrates the diverse conformations that Ras adopts. It is difficult, however, to connect specific structural features with Ras functions. We report the free-energy landscape of Ras·GTP based on extensive explicit solvent simulations. The free-energy map clearly shows that the functional state 2 of Ras·GTP in fact has two distinct substates, denoted here as "Tyr32" and "Tyr32". Unbiased MD simulations show that the two substrates interconvert on the submicrosecond scale in solution, pointing to a novel mechanism for Ras·GTP to selectively interact with GAPs and effectors. This proposal is further supported by time-resolved FTIR experiments, which demonstrate that Tyr32 destabilizes the Ras·GAP complex and facilitates an efficient termination of Ras signaling.
致癌性Ras蛋白采用多种特定构象状态来执行其在信号转导中的功能。通过X射线和核磁共振实验获得的大量Ras结构说明了Ras所采用的多种构象。然而，将特定的结构特征与Ras功能联系起来却很困难。我们基于广泛的显式溶剂模拟报告了Ras·GTP的自由能景观。自由能图清楚地表明，Ras·GTP的功能状态2实际上有两个不同的亚状态，在此表示为“Tyr32”和“Tyr32”。无偏分子动力学模拟表明，这两个亚状态在溶液中以亚微秒尺度相互转换，这为Ras·GTP选择性地与GAP和效应器相互作用指出了一种新机制。时间分辨傅里叶变换红外光谱实验进一步支持了这一观点，该实验表明Tyr32会使Ras·GAP复合物不稳定，并促进Ras信号的有效终止。
