Institute of Biophysics, Department of Physics, Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 1, 60438, Frankfurt/Main, Germany.
Angew Chem Int Ed Engl. 2022 Jan 10;61(2):e202113448. doi: 10.1002/anie.202113448. Epub 2021 Dec 2.
The β-barrel assembly machinery (BAM) consisting of the central β-barrel BamA and four other lipoproteins mediates the folding of the majority of the outer membrane proteins. BamA is placed in an asymmetric bilayer and its lateral gate is suggested to be the functional hotspot. Here we used in situ pulsed electron-electron double resonance spectroscopy to characterize BamA in the native outer membrane. In the detergent micelles, the data is consistent with mainly an inward-open conformation of BamA. The native membrane considerably enhanced the conformational heterogeneity. The lateral gate and the extracellular loop 3 exist in an equilibrium between different conformations. The outer membrane provides a favorable environment for occupying multiple conformational states independent of the lipoproteins. Our results reveal a highly dynamic behavior of the lateral gate and other key structural elements and provide direct evidence for the conformational modulation of a membrane protein in situ.
β-桶装配机器（BAM）由中央β-桶 BamA 和其他四个脂蛋白组成，介导大多数外膜蛋白的折叠。BamA 位于不对称双层中，其侧向门被认为是功能热点。在这里，我们使用原位脉冲电子-电子双共振光谱来表征天然外膜中的 BamA。在去污剂胶束中，数据与 BamA 主要呈向内开放构象一致。天然膜显著增加了构象异质性。侧向门和细胞外环 3 在外膜中不同构象之间处于平衡状态。外膜提供了一个有利于独立于脂蛋白占据多种构象状态的环境。我们的结果揭示了侧向门和其他关键结构元件的高度动态行为，并为膜蛋白在原位的构象调节提供了直接证据。
