title: Characterization of the chromophore of the third rhodopsin-like pigment of Halobacterium halobium and its photoproduct.
abstract: Halobacterium halobium contains at least three retinal-containing pigments: bacteriorhodopsin, halorhodopsin, and a third rhodopsin-like pigment (tR) absorbing at approximately 590 nm, tR590. Illumination of tR590 gives rise to a very long-lived blue absorbing photoproduct, tR370. Using high-performance liquid chromatography we show that the chromophore of tR590 is primarily all-trans retinal and its conversion by light to tR370 causes the chromophore to isomerize primarily to the 13-cis conformation. Irradiation of the tR370 gives rise to a transient photoproduct absorbing at approximately 520 nm that decays back to the initial pigment tR590. In addition to all-trans retinal, the apomembrane of tR can also combine with 13-cis retinal but not with the 9- or 11-cis isomers.
mesh_terms: D001436:Bacteriorhodopsins / Q000502:physiology* / Q000528:radiation effects; D002338:Carotenoids / Q000502:physiology*; D006217:Halobacterium / Q000502:physiology*; D011487:Protein Conformation; D013057:Spectrum Analysis
chemical_list: C042215:slow rhodopsin; D002338:Carotenoids; D001436:Bacteriorhodopsins