title: Architecture of a charge-transfer state regulating light harvesting in a plant antenna protein.
abstract: Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). We found evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a delocalized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can "tune" the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophyll-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Ahn
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Avenson
authors.forename: Matteo
authors.initials: M
authors.lastname: Ballottari
authors.forename: Yuan-Chung
authors.initials: YC
authors.lastname: Cheng
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
mesh_terms: D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002734:Chlorophyll / Q000502:physiology; D000077194:Chlorophyll A; D061146:Chlorophyll Binding Proteins; D060365:Chloroplast Proteins; D004579:Electron Transport; D004594:Electrophysiology; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014975:Lutein / Q000378:metabolism; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000378:metabolism; D012261:Ribonucleoproteins; D013329:Structure-Activity Relationship; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; D060365:Chloroplast Proteins; C490432:LHCB5 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; C529074:RBP29 protein, Arabidopsis; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D024341:Xanthophylls; D065146:Zeaxanthins; D002734:Chlorophyll; C005613:violaxanthin; C037184:chlorophyll b; D014975:Lutein; D000077194:Chlorophyll A