CONVERSION OF BACTERIORHODOPSIN INTO A CHLORIDE-ION PUMP
CONVERSION OF BACTERIORHODOPSIN INTO A CHLORIDE-ION PUMP
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DOI：
10.1126/science.7604281
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发表时间：
1995-07-07
期刊：
影响因子：
56.9
通讯作者：
LANYI, JK
中科院分区：
文献类型：
--
作者：
SASAKI, J;BROWN, LS;LANYI, JK
在光驱动质子泵细菌视紫红质中，质子从视网膜希夫碱转移到天冬氨酸 85 是运输循环的关键反应。在盐视紫红质（一种光驱动的氯离子泵）中，残基 85 的等价物是苏氨酸。当天冬氨酸 85 被苏氨酸取代时，突变的细菌视紫红质在盐盐杆菌中表达时成为氯离子泵，并且像盐视紫红质一样，主动沿与质子泵相反的方向转运氯离子。正如发色团吸收最大值的大幅变化所揭示的那样，氯化物与其结合，并且其光中间体包括毫秒时域内的红移状态，其幅度和衰减率取决于氯化物浓度。因此，细菌视紫红质和盐菌视紫红质具有共同的转运机制，并且残基 85 与视网膜席夫碱的相互作用决定了离子特异性。
In the light-driven proton pump bacteriorhodopsin, proton transfer from the retinal Schiff base to aspartate-85 is the crucial reaction of the transport cycle. In halorhodopsin, a light-driven chloride ion pump, the equivalent of residue 85 is threonine. When aspartate-85 was replaced with threonine, the mutated bacteriorhodopsin became a chloride ion pump when expressed in Halobacterium salinarium and, like halorhodopsin, actively transported chloride ions in the direction opposite from the proton pump. Chloride was bound to it, as revealed by large shifts of the absorption maximum of the chromophore, and its photointermediates included a red-shifted state in the millisecond time domain, with its amplitude and decay rate dependent on chloride concentration. Bacteriorhodopsin and halorhodopsin thus share a common transport mechanism, and the interaction of residue 85 with the retinal Schiff base determines the ionic specificity.