Effect of 13-cis violaxanthin on organization of light harvesting complex II in monomolecular layers.

摘要: Abstract Lutein, neoxanthin and violaxanthin are the main xanthophyll pigment constituents of largest light-harvesting pigment–protein complex photosystem II (LHCII). High performance liquid chromatography analysis revealed photoisomerization LHCII-bound from conformation all-trans to 13-cis 9-cis. Maximally, conversion 15% a cis form could be achieved owing light-driven reactions. The reactions were dark-reversible. isomerization was found driven by blue light, absorbed chlorophylls carotenoids, as well red exclusively chlorophyll pigments. This suggests that is carotenoid triplet-sensitized reaction. monomolecular layer technique applied study effect conformer its de-epoxidized form, zeaxanthin, on organization LHCII compared stereoisomers. specific molecular areas in two-component system composed protein exogenous or zeaxanthin show overadditivity, which an indication xanthophyll-induced disassembly aggregated forms protein. Such not observed layers containing conformers zeaxanthin. 77 K fluorescence emission spectra recorded Langmuir–Blodgett (L–B) films deposited quartz formed with systems isomers opposite effects both aggregation xanthophylls decrease level increased level. calculated efficiency excitation energy transfer assumed remain two steric conformations analyzed basis mean orientation molecules (71° respect normal membrane), determined recently linear dichroism experiments [Gruszecki et al., Biochim. Biophys. Acta 1412 (1999) 173–183]. pool almost independent angle within variability range. In contrast strongly dependent varied between 1.0 (at 67.48°) 0 70.89°). consistent essentially different, possible functions violaxanthin: highly efficient donor (and possibly transmitter other chromophores) purely structure modifier.