Department of Molecular Biosciences, Center for Bioinformatics, The University of Kansas, Lawrence, Kansas, USA.
Biophys J. 2011 Jun 22;100(12):2913-21. doi: 10.1016/j.bpj.2011.05.009.
As the major component of membrane proteins, transmembrane helices embedded in anisotropic bilayer environments adopt preferential orientations that are characteristic or related to their functional states. Recent developments in solid-state nuclear magnetic resonance (SSNMR) spectroscopy have made it possible to measure NMR observables that can be used to determine such orientations in a native bilayer environment. A quasistatic single conformer model is frequently used to interpret the SSNMR observables, but important motional information can be missing or misinterpreted in the model. In this work, we have investigated the orientation of the single-pass transmembrane domain of viral protein "u" (VpuTM) from HIV-1 by determining an ensemble of structures using multiple conformer models based on the SSNMR ensemble dynamics technique. The resulting structure ensemble shows significantly larger orientational fluctuations while the ensemble-averaged orientation is compatible with the orientation based on the quasistatic model. This observation is further corroborated by comparison with the VpuTM orientation from comparative molecular dynamics simulations in explicit bilayer membranes. SSNMR ensemble dynamics not only reveals the importance of transmembrane helix dynamics in interpretation of SSNMR observables, but also provides a means to simultaneously extract both transmembrane helix orientation and dynamics information from the SSNMR measurements.
作为膜蛋白的主要组成部分，嵌入各向异性双层环境中的跨膜螺旋采用优先取向，这些取向与它们的功能状态有关或与其相关。固态核磁共振（SSNMR）光谱学的最新进展使得能够测量可用于在天然双层环境中确定这些取向的 NMR 可观测值。准静态单构象模型常用于解释 SSNMR 可观测值，但模型中可能会缺少或误解重要的运动信息。在这项工作中，我们通过使用基于 SSNMR 整体动力学技术的多个构象模型来确定结构整体，研究了 HIV-1 中病毒蛋白“u”（VpuTM）的单次跨膜结构域的取向。所得的结构整体显示出明显更大的取向波动，而整体平均取向与准静态模型的取向兼容。这一观察结果通过与在明确定义的双层膜中进行的比较分子动力学模拟的 VpuTM 取向的比较得到进一步证实。SSNMR 整体动力学不仅揭示了跨膜螺旋动力学在解释 SSNMR 可观测值中的重要性，而且还提供了一种从 SSNMR 测量中同时提取跨膜螺旋取向和动力学信息的方法。
