Heberle J, Dencher N A
Dept. of Physics, Freie Universität, Berlin, Germany.
FEBS Lett. 1990 Dec 17;277(1-2):277-80. doi: 10.1016/0014-5793(90)80864-f.
The photocycle and the proton pumping kinetics of bacteriorhodopsin, as well as the transfer rate of protons from the membrane surface into the aqueous bulk phase were examined for purple membranes in water and ice. In water, the optical pH indicator pyranine residing in the aqueous bulk phase monitors the H(+)-release later than the pH indicator fluorescein covalently linked to the extracellular surface of BR. In the frozen state, however, pyranine responds to the ejected H+ as fast as fluorescein attached to BR, demonstrating that the surface/bulk transfer is in ice no longer rate limiting. The pumped H+ appears at the extracellular surface during the transition of the photocycle intermediate L550 to the intermediate M412. The Arrhenius plot of the M formation rate suggests that the proton is translocated through the protein via an ice-like structure.
研究了水和冰中紫色膜的细菌视紫红质的光循环、质子泵浦动力学，以及质子从膜表面转移到水相主体中的速率。在水中，水相主体中的光学pH指示剂吡喃荧光素监测H⁺释放的时间比共价连接到细菌视紫红质（BR）细胞外表面的pH指示剂荧光素要晚。然而，在冷冻状态下，吡喃荧光素对释放出的H⁺的响应速度与连接到BR上的荧光素一样快，这表明在冰中表面/主体转移不再是速率限制因素。在光循环中间体L550向中间体M412转变的过程中，泵浦出的H⁺出现在细胞外表面。M形成速率的阿仑尼乌斯图表明，质子通过类似冰的结构穿过蛋白质。
