Bacteriorhodopsin in ice

FEBS Letters

Heberle, Joachim¹  Dencher, Norbert A.¹ 

[1] Dept. of Physics, Biophysics Group, Freie Universität, Arnimallee 14, D-1000 Berlin 33, Germany

关键词: Bacteriorhodopsin;    Purple membrane;    Optical pH indicator;    Proton transfer;    Membrane surface;    Flash spectroscopy;   

DOI  :  10.1016/0014-5793(90)80864-F

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 in 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.

【 授权许可】

Unknown