Transient channel-opening in bacteriorhodopsin: an EPR study.
Transient channel-opening in bacteriorhodopsin: an EPR study.
复制标题
细菌视紫红质的瞬时通道开放：一项 EPR 研究。
DOI：
10.1006/jmbi.1997.1362
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发表时间：
1997
影响因子：
5.6
通讯作者：
Shin,YK
中科院分区：
文献类型：
--
作者：
Thorgeirsson,TE;Xiao,W;Brown,LS;Needleman,R;Lanyi,JK;Shin,YK
离子跨膜的主动转移需要泵内的离子结合部位交替进入两个膜表面。细菌视紫红质(BR)是盐生盐生杆菌中光驱动的质子泵，它的质子转运涉及到位于中心位置的视网膜Schiff碱的这种可及性的变化。BR光循环中的这一关键事件确保了质子在细胞外侧释放和从细胞质一侧吸收。为了研究蛋白质构象变化在这种再质子化开关中的作用，在BR的细胞质螺旋间环中的工程半胱氨酸残基对上贴上了自旋标记。观察到了光诱导的EF螺旋环上的自旋标记与AB或CD螺旋环上的标记之间的距离的变化，并用时间分辨电子顺磁共振(EPR)光谱监测了光激活后的变化。在光循环过程中，这两个距离都瞬时增加了约5？这种开放发生在质子释放和吸收之间，并且可能是在质子释放到细胞外侧后改变视网膜Schiff碱基到细胞质表面的可及性的构象开关。
Active translocation of ions across membranes requires alternating access of the ion binding site inside the pump to the two membrane surfaces. Proton translocation by bacteriorhodopsin (bR), the light-driven proton pump in Halobacterium salinarium, involves this kind of a change in the accessibility of the centrally located retinal Schiff base. This key event in bR’s photocycle ensures that proton release occurs to the extracellular side and proton uptake from the cytoplasmic side. To study the role of protein conformational changes in this reprotonation switch, spin labels were attached to pairs of engineered cysteine residues in the cytoplasmic interhelical loops of bR. Light-induced changes in the distance between a spin label on the EF interhelical loop and a label on either the AB or the CD interhelical loop were observed, and the changes were monitored following photoactivation with time-resolved electron paramagnetic resonance (EPR) spectroscopy. Both distances increase transiently by about 5 Å during the photocycle. This opening occurs between proton release and uptake, and may be the conformational switch that changes the accessibility of the retinal Schiff base to the cytoplasmic surface after proton release to the extracellular side.