The main thylakoid membrane lipid monogalactosyldiacylglycerol (MGDG) promotes the de-epoxidation of violaxanthin associated with the light-harvesting complex of photosystem II (LHCII)

摘要: In higher plants, the major part of xanthophyll cycle pigment violaxanthin (Vx) is non-covalently bound to main light-harvesting complex PSII (LHCII). Under saturating light conditions Vx has be released from its binding site into surrounding lipid phase, where it converted zeaxanthin (Zx) by enzyme de-epoxidase (VDE). present study we investigated influence thylakoid lipids on de-epoxidation Vx, which was still associated with LHCII. We isolated LHCII different concentrations native, endogenous and sucrose gradient centrifugation or successive cation precipitation. Analysis preparations showed that concentration LHCII-associated correlated monogalactosyldiacylglycerol (MGDG) complexes. Decreases in MGDG content led a diminished concentration, indicating total pool located an phase LHCII, whereas another apoproteins. further studied convertibility in-vitro assays addition VDE. observed efficient almost complete conversion fractions containing high amounts MGDG. low exhibited strongly reduced de-epoxidation, could increased exogenous, pure The saturated at much lower compared isolated, exogenous MGDG, needed for optimal VDE activity employing Vx.