Influence of the Chromophore Retinal and the State of Aggregation on the Proton/Hydroxyl Ion Flux Across Bacteriorhodopsin
The influence of the chromophore retinal in bacteriorhodopsin on the passive proton/hydroxide ion flux through the protein was examined. Bacteriorhodopsin was reconstituted into unilamellar lipid vesicles. Transmembrane pH-gradients were quickly established across the vesicular membrane and the induced kinetics of the fluorescence changes of the entrapped dye pyranine were compared for vesicles with incorporated native, chromophore-free, and regenerated protein. The H+/OH- diffusion across the apoprotein was considerably faster than through the protein containing covalently bound retinal. A linear dependence between the ΔpH decay time and the degree of regeneration was observed.
KeywordsPurple Membrane Protein Moiety Vesicular Membrane Chromophore Retinal Halobacterium Halobium
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