Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
Institute of Biophysical Chemistry, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Straße 9, 60438, Frankfurt am Main, Germany.
Angew Chem Int Ed Engl. 2020 Nov 16;59(47):20965-20972. doi: 10.1002/anie.202004393. Epub 2020 Sep 7.
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR.
为了在光驱动质子泵菌视紫红质（bR）中实现高效质子泵，该蛋白必须与视黄醛紧密偶联，以快速将视黄醛异构化转化为蛋白结构重排。在暗适应状态下，确定了嵌入脂质纳米圆盘的 bR 的甲基动力学，发现其在胞质侧大部分有序。bR 的 M145A 突变体中的甲基，其质子泵活性仅残留 10%，其有序性较差，这表明 bR 腔胞质侧侧链动力学与质子泵活性之间存在联系。此外，还间接观察到 bR 腔细胞外侧残基的慢构象交换，归因于芳环的低频运动。这可能与水网络的重组有关。这些观察结果为之前未描述的 bR 基态不同时间尺度的平衡动力学提供了详细的描述。
