Comparison of the Two Retinal Proteins Bacteriorhodopsin and Halorhodopsin
Two retinal proteins act as light-driven pumps in halobacteria. Bacteriorhodopsin (BR) translocates protons to the medium and halorhodopsin (HR) transports chloride into the cytoplasma. Bacteriorhodopsin’s functional and structural properties are well known. Transport is mediated by a photochemical cycle of the retinal chromophore accompanied by trans to cis isomerization and a reversible deprotonation of its Schiff base. Spectroscopy in combination with the use of retinal analogue compounds demonstrated that the trans to cis isomerization is connected to the primary photochemical reaction (1).
KeywordsSchiff Base Retinal Protein Black Lipid Membrane Retinal Chromophore Halobacterium Halobium
- 5).S. Smith, M. Marvin, R. Bogomolni and R. Mathies, Structure of the Retinal Chromophore in the HR,,, Form of Halorhodopsin. J. Biol. Chem. 259:2326 (1984).Google Scholar
- 6).P. Hegemann, D. Oesterhelt and E. Bamberg, The Transport Activity of the Light-driven Chloride Pump Halorhodopsin is Regulated by Green and Blue Light. BBA (in press, issue Sept./Oct. 1985).Google Scholar
- 7).P. Hegemann, D. Oesterhelt and M. Steiner, The Photocycle of the Chloride Pump Halorhodopsin. I. Azide Catalyzed Deprotonation of the Chromophore Intermediates Inactivating the Pump. EMBO J. (in press, issue Sept. 1985).Google Scholar
- 8).D. Oesterhelt and P. Hegemann, The Photocycle of the Chloride Pump Halorhodopsin. II. Quantum Yields and a Kinetic Model. EMBO J. (in press, issue Sept. 1985).Google Scholar
- 9).D. Oesterhelt, P. Hegemann, P. Tavan and K. Schulten, A Model for Ion Translocation in Halorhodopsin by trans-cis Isomerization of its Retinal Moiety (in preparation).Google Scholar