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Article Dans Une Revue Photosynthesis Research Année : 2018

Pigment configuration in the light-harvesting protein of the xanthophyte alga Xanthonema debile

Résumé

The soil chromophyte alga Xanthonema (X.) debile contains only non-carbonyl carotenoids and Chl-a. X. debile has an antenna system denoted Xanthophyte light-harvesting complex (XLH) that contains the carotenoids diadinoxanthin, heteroxanthin, and vaucheriaxanthin. The XLH pigment stoichiometry was calculated by chromatographic techniques and the pigment-binding structure studied by resonance Raman spectroscopy. The pigment ratio obtained by HPLC was found to be close to 8:1:2:1 Chl-a:heteroxanthin:diadinoxanthin:vaucheriaxanthin. The resonance Raman spectra suggest the presence of 8-10 Chl-a, all of which are 5-coordinated to the central Mg, with 1-3 Chl-a possessing a macrocycle distorted from the relaxed conformation. The three populations of carotenoids are in the all-trans configuration. Vaucheriaxanthin absorbs around 500-530nm, diadinoxanthin at 494nm and heteroxanthin at 487nm at 4.5K. The effective conjugation length of heteroxanthin and diadinoxanthin has been determined as 9.4 in both cases; the environment polarizability of the heteroxanthin and diadinoxanthin binding pockets is 0.270 and 0.305, respectively.
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Dates et versions

hal-02183691 , version 1 (15-07-2019)

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Simona Streckaite, Zdenko Gardian, Fei Li, Andrew A. Pascal, Radek Litvin, et al.. Pigment configuration in the light-harvesting protein of the xanthophyte alga Xanthonema debile. Photosynthesis Research, 2018, 138 (2), pp.139--148. ⟨10.1007/s11120-018-0557-1⟩. ⟨hal-02183691⟩
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