Conformational dynamics of a G-protein α subunit is tightly regulated by nucleotide binding
Conformational dynamics of a G-protein α subunit is tightly regulated by nucleotide binding
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DOI：
10.1073/pnas.1604125113
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发表时间：
2016-06-28
影响因子：
11.1
通讯作者：
Hagn, Franz
中科院分区：
文献类型：
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作者：
Goricanec, David;Stehle, Ralf;Hagn, Franz
异源三聚体G蛋白在G蛋白偶联受体（GPCR）激活启动的信号转导通路中起着关键作用。激动剂受体结合导致GDP与GTP交换以及G α亚基从异三聚体G蛋白中解离，从而导致下游信号传导。在这里，我们研究了G蛋白α亚基在其载脂蛋白和核苷酸结合形式的内部流动性，并在多个时间尺度上使用溶液NMR，小角X射线散射和分子动力学模拟表征其动力学特征。我们发现，GTP类似物的结合导致G α亚结构域的刚性和封闭的排列，而载脂蛋白和GDP结合的形式是相当开放和动态的。此外，我们能够检测到两种构象状态的G α Ras结构域在缓慢的交换，其人口的调节结合到核苷酸和GPCR。这些构象状态之一，即开放状态，与GPCR结合;第二种构象，即闭合状态，与受体没有相互作用。与GPCR的结合稳定了开放状态。这项研究提供了一个深入的分析的构象景观和开关功能的G蛋白α亚基和GPCR的影响，景观。
Heterotrimeric G proteins play a pivotal role in the signal-transduction pathways initiated by G-protein-coupled receptor (GPCR) activation. Agonist-receptor binding causes GDP-to-GTP exchange and dissociation of the G alpha subunit from the heterotrimeric G protein, leading to downstream signaling. Here, we studied the internal mobility of a G-protein alpha subunit in its apo and nucleotide-bound forms and characterized their dynamical features at multiple time scales using solution NMR, small-angle X-ray scattering, and molecular dynamics simulations. We find that binding of GTP analogs leads to a rigid and closed arrangement of the G alpha subdomain, whereas the apo and GDP-bound forms are considerably more open and dynamic. Furthermore, we were able to detect two conformational states of the G alpha Ras domain in slow exchange whose populations are regulated by binding to nucleotides and a GPCR. One of these conformational states, the open state, binds to the GPCR; the second conformation, the closed state, shows no interaction with the receptor. Binding to the GPCR stabilizes the open state. This study provides an in-depth analysis of the conformational landscape and the switching function of a G-protein alpha subunit and the influence of a GPCR in that landscape.