The proton pump bacteriorhodopsin is a photoreceptor for signal transduction in Halobacterium halobium

• Published in: FEBS letters Vol. 295; no. 1; pp. 223 - 226
• Main Authors: Bibikov, Sergei I., Grishanin, Ruslan N., Marwan, Wolfgang, Oesterhelt, Dieter, Skulachev, Vladimir P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 16.12.1991; Elsevier
• Subjects: Analytical, structural and metabolic biochemistry; Bacteriorhodopsin; Bacteriorhodopsins - physiology; Biological and medical sciences; Darkness; Fundamental and applied biological sciences. Psychology; Halobacterium salinarum - physiology; Kinetics; Light; Models, Biological; Non metallic chromoproteins, photoproteins; Photophobic response; Photoreceptor Cells; Proteins; Proton-motive force sensor; Signal Transduction; Bacteriorhodopsin; Photophobic response; Proton-motive force sensor; Signal transduction; Archaeobacteria; Photoreceptor; Photokinesis; Bacteria; Proton gradient; Halobacteriaceae; Gene expression; Motive force; Halobacterium halobium
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(91)81423-6

Halobacterium halobium swims by rotating its polarly inserted flagellar bundle. The cells are attracted by green-to-orange light which they can use for photophosphorylation but flee damaging blue or ultraviolet light. It is generally believed that this kind of ‘colour vision’ is achieved by the combined action of two photoreceptor proteins, sensory rhodopsins-I and -II, that switch in the light the rotational sense of the bundle and in consequence the swimming direction of a cell. By expressing the bacteriorhodopsin gene in a photoreceptor-negative background we have now demonstrated the existence of a proton-motive force sensor (protometer) and the function of bacteriorhodopsin as an additional photoreceptor covering the high intensity range. When the bacteriorhodopsin-generated proton-motive force drops caused by a sudden decrease in light intensity, the cells respond by reversing their swimming direction. This response does not occur when the proton-motive force is saturated by respiration or fermentation.