Proton Translocation by Bacteriorhodopsin in Model Systems
Bacteriorhodopsin is a rhodopsin-like pigment found in the cell membrane of halobacteria. It occurs in discrete patches with a planar hexagonal lattice structure known as the purple membrane (Oesterhelt and Stoeckenius, 1971; Blaurock and Stoeckenius, 1971). When bacteriorhodopsin absorbs light, it undergoes a rapid cyclic photoreaction during which it translocates a proton across the membrane (Lozier et al, 1975; Lozier et al, 1976). In continuous light it acts as a light-driven proton pump generating a proton gradient and membrane potential. The cells can use the energy stored in the electrochemical gradient to synthesize ATP (Oester-helt and Stoeckenius, 1973; Bogomolni et al, 1976; Danon and Stoeckenius, 1974). In intact cells it is difficult to measure parameters such as rapid absorption changes of the pigment, intracellular ion concentrations, and membrane potential, which are necessary to quantitate the light energy conversion in this system. Moreover, the energy metabolism of halobacteria has not been investigated in detail and contributions from other energy sources are difficult to evaluate. Reconstitution of the bacteriorhodopsin function in a well-characterized model system avoids most of the difficulties encountered in work with intact cells.
KeywordsLipid Vesicle Proton Acceptor Planar Film Fracture Face Soybean Lecithin
Unable to display preview. Download preview PDF.
- Bogomolni, R. A., R. A. Baker, R. H. Lozier and W. Stoeckenius, Light-driven proton translocations in Halobacterium halobium,Biochim. Biophys. Acta, in press, 1976.Google Scholar
- Drachev, L. A., A. A. Jasaitis, A. D. Kaulen, A. A. Kondrashin, E. A. Liberman, I. B. Nemecek, S. A. Ostroumov, A. Yu. Semenov and V. P. Skulachev, Direct measurement of electric current generation by cytochrome oxidase, H+-ATPase and bacteriorhodopsin, Nature 249, 321, 1974a.PubMedCrossRefGoogle Scholar
- Hwang, S.-B., J. I. Korenbrot and W. Stoeckenius, Light-dependent proton transport by bacteriorhodopsin incorporated in an interface film, J. Supramolecular Structure, in press, 1976.Google Scholar
- Lozier, R. H., W. Niederberger, R. A. Bogomolni, S.-B. Hwang and W. Stoeckenius, Kinetics and stoichiometry of light-induced proton release and uptake from purple membrane fragments, Halobacterium halobium cell envelopes, and phospholipid vesicles containing oriented purple membrane, Biochim. Biophys. Acta, in press, 1976.Google Scholar
- Oesterhelt, D. and W. Stoeckenius, Isolation of the cell membrane of Halobacterium halobium and its fractionation into red and purple membrane, in Methods in Enzymology Volume XXXI, Biomembranes Part A, ed. S. Fleischer and L. Packer, pp. 667678, Academic Press, New York-San Francisco-London, 1974.Google Scholar