A Protein Environment-Modulated Energy Dissipation Channel in LHCII Antenna Complex
Francesco Saccon,
Milan Durchan,
David Bína,
Christopher D.P. Duffy,
Alexander V. Ruban,
Tomáš Polívka
Affiliations
Francesco Saccon
Queen Mary University of London, School of Biological and Chemical Sciences, Mile End Road, E1 4NS London, UK
Milan Durchan
University of South Bohemia, Institute of Physics, Faculty of Science, České Budějovice, Czech Republic; Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, České Budějovice, Czech Republic
David Bína
University of South Bohemia, Institute of Chemistry, Faculty of Science, České Budějovice, Czech Republic; Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, České Budějovice, Czech Republic
Christopher D.P. Duffy
Queen Mary University of London, School of Biological and Chemical Sciences, Mile End Road, E1 4NS London, UK
Alexander V. Ruban
Queen Mary University of London, School of Biological and Chemical Sciences, Mile End Road, E1 4NS London, UK
Tomáš Polívka
University of South Bohemia, Institute of Physics, Faculty of Science, České Budějovice, Czech Republic; Corresponding author
Summary: The major light-harvesting complex of photosystem II (LHCII) is the main contributor to sunlight energy harvesting in plants. The flexible design of LHCII underlies a photoprotective mechanism whereby this complex switches to a dissipative state in response to high light stress, allowing the rapid dissipation of excess excitation energy (non-photochemical quenching, NPQ). In this work, we locked single LHCII trimers in a quenched conformation after immobilization of the complexes in polyacrylamide gels to impede protein interactions. A comparison of their pigment excited-state dynamics with quenched LHCII aggregates in buffer revealed the presence of a new spectral band at 515 nm arising after chlorophyll excitation. This is suggested to be the signature of a carotenoid excited state, linked to the quenching of chlorophyll singlet excited states. Our data highlight the marked sensitivity of pigment excited-state dynamics in LHCII to structural changes induced by the environment.
