Light- and pH-dependent conformational changes in protein structure induce strong bending of purple membranes--active membranes studied by cryo-SEM.
Light- and pH-dependent conformational changes in protein structure induce strong bending of purple membranes--active membranes studied by cryo-SEM.
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蛋白质结构中光和 pH 依赖性构象变化引起紫色膜的强烈弯曲——通过冷冻扫描电镜研究活性膜
DOI：
10.1021/jp803510t
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
N. Hampp
中科院分区：
文献类型：
--
作者：
D. Rhinow;N. Hampp
细菌视紫红质（BR）在光循环和质子跨膜转运过程中会发生构象变化。这是第一次，我们可以证明，通过直接成像的自由悬浮的原生紫膜（PMs）的平面盘状形状的PMs的变化显着，只要大多数的BR的特征在于由去质子化的席夫碱的状态。用BR-D96N型突变的BR容易观察到光诱导的形状变化，所有变体都显示出增加的M2寿命。另一方面，用含有BR-D85T型突变BR的PM通过pH变化诱导大规模形状变化，其中Asp85被替换为中性氨基酸。在这样的PM中，所有BR同时滴定，并且所得膜的形状仅取决于初始形状。由于大多数处于"平坦"状态的PM或多或少是圆盘，因此弯曲膜通常包括碗状和管状弯曲结构。这里提出的方法，使一个从“宏观”，容易获得的数据，如在低温扫描电镜中观察到的曲率半径的单分子水平上的膜包埋BR的大小变化。BR作为pH控制和/或光控制的微尺度生物致动器的潜力需要进一步考虑。
Bacteriorhodopsin (BR) undergoes a conformational change during the photocycle and the proton transport through the membrane. For the first time, we could demonstrate by direct imaging of freely suspended native purple membranes (PMs) that the flat disk-like shape of PMs changes dramatically as soon as most of the BRs are in a state characterized by a deprotonated Schiff base. Light-induced shape changes are easily observed with mutated BRs of the BR-D96N type, i.e., all variants which show an increased M2lifetime. On the other hand, large-scale shape changes are induced by pH changes with PM containing mutated BRs of the BR-D85T type, where Asp85 is replaced for a neutral amino acid. In such PMs, all BRs are titrated simultaneously and the resulting shape of the membranes depends on the initial shape only. As the majority of PMs in the “flat” state are more or less round disks, the bent membranes often comprise bowl-like and tube-like bent structures. The method presented here enables one to derive size changes of membrane-embedded BRs on the single molecule level from “macroscopic”, easily accessible data like the curvature radii observed in cryo-SEM. The potential of BR as a pH-controlled and/or light-controlled microscaled biological actuator needs further consideration.