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Photosynth Res. 2018 Nov;138(2):139-148. doi: 10.1007/s11120-018-0557-1. Epub 2018 Jul 13.

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

Author information

1
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
2
Biology Centre, Czech Academy of Sciences, Branisovska 31, 370 05, Ceske Budejovice, Czech Republic.
3
Faculty of Science, University of South Bohemia, Branisovska 1760, 370 05, Ceske Budejovice, Czech Republic.
4
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, People's Republic of China.
5
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France. manuel.llansola@i2BC.paris-saclay.fr.

Abstract

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 500-530 nm, diadinoxanthin at 494 nm and heteroxanthin at 487 nm at 4.5 K. 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.

KEYWORDS:

Algae; Carotenoids; Chl-a; Diadinoxanthin; Heteroxanthin; Light-harvesting complex; Resonance Raman

PMID:
30006883
DOI:
10.1007/s11120-018-0557-1
[Indexed for MEDLINE]

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