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

Archive ouverte

Streckaite, Simona | Gardian, Zdenko | Li, Fei | Pascal, Andrew A. | Litvin, Radek | Robert, Bruno | Llansola-Portoles, Manuel J.

Edité par CCSD ; Springer Verlag -

International audience. 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.

• Description
• Sujet/Public
• Outil
• Outil d'anticipation
• Mémoire et thèse
• Gestion