Haupts U, Bamberg E, Oesterhelt D
Max-Plank-Institut für Biochemie, Martinsried, Germany.
EMBO J. 1996 Apr 15;15(8):1834-41.
The membrane-bound complex between sensory rhodopsin I (SRI) and its transducer HtrI forms the functional photoreceptor unit that allows transmission of light signals to the flagellar motor. Although being a photosensor, SRI, the mutant SRI-D76N and the HtrI-SRI complex can transport protons, as we demonstrate by using the sensitive and ion-specific black lipid membrane technique. SRI sustains an orange light-driven (one-photon-driven) outward proton transport which is enhanced by additional blue light (two-photon-driven). The vectoriality of the two-photon-driven transport could be reversed at neutral pH from the outward to the inward direction by switching the cut-off wavelength of the long wavelength light from 550 to 630 nm. The cut-off wavelength determining the reversal point decreases with decreasing pH. The currents could be enhanced by azide. A two-photon-driven inward proton transport by SRI-D76N (catalyzed by azide) and by the complex HtrI-SRI is demonstrated. The influence of pH and azide concentration on the rise and decay kinetics of the SRI380 intermediate is analyzed. The different modes of proton translocation of the SRI species are discussed on the basis of a general model of proton translocation of retinal proteins and in the context of signal transduction.
感官视紫红质I（SRI）与其转导蛋白HtrI之间的膜结合复合物形成了功能性光感受器单元，该单元可将光信号传递至鞭毛马达。尽管SRI作为一种光传感器，但我们通过使用灵敏且离子特异性的黑脂质膜技术证明，SRI、突变体SRI-D76N以及HtrI-SRI复合物均可运输质子。SRI维持着橙色光驱动（单光子驱动）的外向质子运输，额外的蓝光（双光子驱动）可增强这种运输。在中性pH条件下，通过将长波长光的截止波长从550 nm切换至630 nm，双光子驱动运输的矢量性可从外向内方向反转。决定反转点的截止波长随pH降低而减小。叠氮化物可增强电流。本文证明了SRI-D76N（由叠氮化物催化）和HtrI-SRI复合物存在双光子驱动的内向质子运输。分析了pH和叠氮化物浓度对SRI380中间体上升和衰减动力学的影响。基于视网膜蛋白质子转运的通用模型并结合信号转导背景，讨论了SRI物种质子转运的不同模式。
