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1Author    N. Orbert, A. Dencher, Eilo HildebrandRequires cookie*
 Title    Sensory Transduction in Halobacterium halobium: Retinal Protein Pigment Controls UV-Induced Behavioral Response  
 Abstract    Both photosystems, PS 370 and PS 565, controlling behavioral responses in H alobacterium halo-bium [E. Hildebrand and N. Dencher, Nature 2 5 7 ,4 6 — 48 (1975)] are reversibly inhibited when bacteria are grown in the presence o f 1 mM nicotine which is known to block biosynthesis o f reti­ nal. Photobehavior can be restored within som e minutes to hours by adding retinal to nicotine-treated bacteria, PS 370 thereby reappearing earlier than PS 565. The reconstitution rate depends on the concentration and on the kind o f retinal isomers applied. A \\-trans retinal is m ost effective. PS 370 becomes fully sensitive if reconstituted in the presence o f nicotine. This rules out the possi­ bility that the alkaloid may directly inhibit steps o f signal transmission follow ing photoreception. The action spectrum o f PS 370 regenerated with retinal alone o f H. h., strain RjLg (a mutant deficient in carotenoids), fails to show all secondary peaks around 450 nm which in strain Rj occur besides the prominent maximum at 370 nm. A ddition o f carotenoids (m ainly a-bacterioruberin) to reconstituted cells o f R ,L3 restores the sensitivity in that spectral region. Carotenoids or flavin solely added to nicotine-treated bacteria cannot restore photobehavior. We conclude that the active pigm ent o f PS 370, which m ediates the photophobic response to increase o f light intensity (step-up response), represents a retinal protein com plex and that carote­ noids participate in photoreceptor function as accessory pigments. The biochem ical relation o f the UV-absorbing retinal protein com plex to bacteriorhodopsin is discussed. 
  Reference    Z. Naturforsch. 34c, 841 (1979); received June 5/July 6 1979 
  Published    1979 
  Keywords    Bacteria, Photophobic Response, Bacteriorhodopsin, Carotenoids, Accessory Pigment 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0841.pdf 
 Identifier    ZNC-1979-34c-0841 
 Volume    34