Xanthorhodopsin: a proton pump with a light-harvesting carotenoid antenna.
Energy transfer from light-harvesting carotenoids to chlorophyll is common in photosynthesis, but such antenna pigments have not been observed in retinal-based ion pumps and photoreceptors. Here we describe xanthorhodopsin, a proton-pumping retinal protein/carotenoid complex in the eubacterium Salinibacter ruber. The wavelength dependence of the rate of pumping and difference absorption spectra measured under a variety of conditions indicate that this protein contains two chromophores, retinal and the carotenoid salinixanthin, in a molar ratio of about 1:1. The two chromophores interact strongly, and light energy absorbed by the carotenoid is transferred to the retinal with a quantum efficiency of approximately 40%. The antenna carotenoid extends the wavelength range of the collection of light for uphill transmembrane proton transport.
Balashov
Sergei P
SP
University of California, Irvine, CA 92697, USA. balashov@uci.edu
Imasheva
Eleonora S
ES
Boichenko
Vladimir A
VA
Antón
Josefa
J
Wang
Jennifer M
JM
Lanyi
Janos K
JK
D000595:Amino Acid Sequence; D041963:Bacteroidetes / Q000737:chemistry* / Q000378:metabolism; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism; D004735:Energy Transfer; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D019811:Hydroxylamine / Q000494:pharmacology; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010101:Oxygen Consumption; D017494:Proton Pumps / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012172:Retinaldehyde / Q000737:chemistry / Q000378:metabolism; D025604:Rhodopsins, Microbial / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis
D006027:Glycosides; D045342:Light-Harvesting Protein Complexes; D017494:Proton Pumps; D025604:Rhodopsins, Microbial; C470489:salinixanthin; D019811:Hydroxylamine; D002338:Carotenoids; D012172:Retinaldehyde