Hydrophobic Gate of Mechanosensitive Channel of Large Conductance in Lipid Bilayers Revealed by Solid-State NMR Spectroscopy
Hydrophobic Gate of Mechanosensitive Channel of Large Conductance in Lipid Bilayers Revealed by Solid-State NMR Spectroscopy
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固态核磁共振波谱揭示脂质双层中大电导机械敏感通道的疏水门
DOI：
10.1021/acs.jpcb.0c07487
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发表时间：
2021
影响因子：
3.3
通讯作者：
Yang Jun
中科院分区：
文献类型：
--
作者：
Zhang Xuning;Zhang Yan;Tang Siyang;Ma Shaojie;Shen Yang;Chen Yanke;Tong Qiong;Li Yuezhou;Yang Jun
细菌大电导机械敏感性通道（MscL）作为一个减压安全阀，防止细胞在突然低渗休克时裂解。MscL的疏水门在关闭状态下对离子和水分子的渗透形成屏障，并可以切换到打开状态以释放溶液和离子。目前，门构成残基和这些残基在MscL的疏水门的功能作用仍然是难以捉摸的和有争议的。在这里，我们采用魔角旋转固态核磁共振（ssNMR）技术和功能分析，以调查MscL的疏水门醋酸甲烷八叠球菌（Ma-MscL）的脂质双层。我们获得了Ma-MscL的~ 70%残基的化学位移归属，并预测了其三维结构。基于结构表征，我们通过使用ssNMR H/D交换和水编辑实验检测跨膜孔中的水分布来鉴定跨膜螺旋1中的残基I21-T30构成疏水门。通过使用ssNMR结构表征和功能测定，我们揭示了Ma-MscL的每个亚基中的F23的芳环的包装对疏水门是至关重要的，并且其他功能上重要的残基A22和G26的亲水取代通过减弱F23的收缩的疏水性来调节通道门控。
The bacterial mechanosensitive channel of large conductance (MscL) functions as a pressure-relief safety valve to prevent cells from lysing during sudden hypo-osmotic shock. The hydrophobic gate of MscL in the closed state forms a barrier to the permeation of ions and water molecules and can be switched to the open state for releasing solutions and ions. Currently, the gate-constituting residues and the functional role of these residues in the hydrophobic gate of MscL remain elusive and controversial. Here, we employ magic angle spinning solid-state nuclear magnetic resonance (ssNMR) techniques and functional assays to investigate the hydrophobic gate of MscL fromMethanosarcina acetivorans(Ma-MscL) in lipid bilayers. We obtain chemical shift assignments of ∼70% residues of Ma-MscL and predict its 3D structure. Based on the structural characterization, we identify that the residues I21–T30 in the transmembrane helix 1 constitute the hydrophobic gate by detecting water distributions in the transmembrane pore using ssNMR H/D exchange and water-edited experiments. By using ssNMR structural characterization and functional assays, we reveal that the packing of aromatic rings of F23 in each subunit of Ma-MscL is critical to the hydrophobic gate, and hydrophilic substitutions of the other functionally important residues A22 and G26 modulate channel gating by attenuating hydrophobicity of constriction of F23.