Perozo Eduardo, Cortes D Marien, Sompornpisut Pornthep, Kloda Anna, Martinac Boris
Department of Molecular Physiology and Biological Physics, and Center for Structural Biology, University of Virginia, Charlottesville, Virginia 22906, USA.
Nature. 2002 Aug 29;418(6901):942-8. doi: 10.1038/nature00992.
Mechanosensitive channels act as membrane-embedded mechano-electrical switches, opening a large water-filled pore in response to lipid bilayer deformations. This process is critical to the response of living organisms to direct physical stimulation, such as in touch, hearing and osmoregulation. Here, we have determined the structural rearrangements that underlie these events in the large prokaryotic mechanosensitive channel (MscL) using electron paramagnetic resonance spectroscopy and site-directed spin labelling. MscL was trapped in both the open and in an intermediate closed state by modulating bilayer morphology. Transition to the intermediate state is characterized by small movements in the first transmembrane helix (TM1). Subsequent transitions to the open state are accompanied by massive rearrangements in both TM1 and TM2, as shown by large increases in probe dynamics, solvent accessibility and the elimination of all intersubunit spin-spin interactions. The open state is highly dynamic, supporting a water-filled pore of at least 25 A, lined mostly by TM1. These structures suggest a plausible molecular mechanism of gating in mechanosensitive channels.
机械敏感通道作为嵌入膜中的机电开关，响应脂质双层变形时打开一个充满水的大孔。这一过程对于生物体对直接物理刺激的反应至关重要，例如在触觉、听觉和渗透调节中。在这里，我们使用电子顺磁共振光谱和定点自旋标记确定了大型原核机械敏感通道（MscL）中这些事件背后的结构重排。通过调节双层形态，MscL被捕获在开放状态和中间关闭状态。向中间状态的转变的特征是第一个跨膜螺旋（TM1）中的微小运动。随后向开放状态的转变伴随着TM1和TM2的大量重排，如探针动力学、溶剂可及性的大幅增加以及所有亚基间自旋-自旋相互作用的消除所示。开放状态高度动态，支持至少25埃的充满水的孔，主要由TM1排列。这些结构提示了机械敏感通道门控的一种合理分子机制。
