Cis-trans-isomerization of violaxanthin in LHC II: violaxanthin isomerization cycle within the violaxanthin cycle

摘要

Chlorophyll fluorescence excitation and emission spectroscopy, electron absorption spectroscopy and resonance Raman spectrometry of light-harvesting pigment-protein complex of Photosystem II (LHC II), isolated and incorporated to liposomes, indicate that a carotenoid pigment violaxanthin is present in this complex in conformation 15, 15'-cis. Light-induced cis-trans-isomerization of violaxanthin is combined with an energetic uncoupling of this antenna pigment from chlorophyll and is interpreted in terms of detachment of this carotenoid from protein - the process of making violaxanthin available for de-epoxidation within the lipid phase of the thylakoid membrane. It is also demonstrated that the process of heat-induced detachment of violaxanthin from LHC II is not combined with a cis-trans- isomerization.