Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Biophys J. 2011 Oct 19;101(8):1905-12. doi: 10.1016/j.bpj.2011.09.026.
Pentameric ligand-gated ion channels are targets of general anesthetics. Although the search for discrete anesthetic binding sites has achieved some degree of success, little is known regarding how anesthetics work after the events of binding. Using the crystal structures of the bacterial Gloeobacter violaceus pentameric ligand-gated ion channel (GLIC), which is sensitive to a variety of general anesthetics, we performed multiple molecular dynamics simulations in the presence and absence of the general anesthetic isoflurane. Isoflurane bound to several locations within GLIC, including the transmembrane pocket identified crystallographically, the extracellular (EC) domain, and the interface of the EC and transmembrane domains. Isoflurane also entered the channel after the pore was dehydrated in one of the simulations. Isoflurane disrupted the quaternary structure of GLIC, as evidenced in a striking association between the binding and breakage of intersubunit salt bridges in the EC domain. The pore-lining helix experienced lateral and inward radial tilting motion that contributed to the channel closure. Isoflurane binding introduced strong anticorrelated motions between different subunits of GLIC. The demonstrated structural and dynamical modulations by isoflurane aid in the understanding of the underlying mechanism of anesthetic inhibition of GLIC and possibly other homologous pentameric ligand-gated ion channels.
五聚体配体门控离子通道是全身麻醉剂的作用靶点。尽管寻找离散的麻醉结合位点已经取得了一定的成功，但对于结合发生后麻醉剂如何发挥作用，我们知之甚少。我们利用对多种全身麻醉剂敏感的细菌 Gloeobacter violaceus 五聚体配体门控离子通道（GLIC）的晶体结构，在存在和不存在全身麻醉剂异氟烷的情况下进行了多次分子动力学模拟。异氟烷结合到 GLIC 的多个位置，包括晶体学上确定的跨膜口袋、细胞外（EC）结构域以及 EC 和跨膜结构域的界面。在其中一个模拟中，异氟烷还在孔道脱水后进入了通道。异氟烷破坏了 GLIC 的四级结构，这表现在 EC 结构域中结合和打破亚基间盐桥方面存在明显的关联。孔道衬里的螺旋经历了侧向和向内的径向倾斜运动，导致通道关闭。异氟烷结合引入了 GLIC 不同亚基之间强烈的反相关运动。异氟烷所表现出的结构和动力学调节有助于理解麻醉抑制 GLIC 及可能其他同源五聚体配体门控离子通道的潜在机制。
