title: Lutein can act as a switchable charge transfer quencher in the CP26 light-harvesting complex.
abstract: Energy-dependent quenching of excitons in photosystem II of plants, or qE, has been positively correlated with the transient production of carotenoid radical cation species. Zeaxanthin was shown to be the donor species in the CP29 antenna complex. We report transient absorbance analyses of CP24 and CP26 complexes that bind lutein and zeaxanthin in the L1 and L2 domains, respectively. For CP24 complexes, the transient absorbance difference profiles give a reconstructed transient absorbance spectrum with a single peak centered at approximately 980 nm, consistent with zeaxanthin radical cation formation. In contrast, CP26 gives constants for the decay components probed at 940 and 980 nm of 144 and 194 ps, a transient absorbance spectrum that has a main peak at 980 nm, and a substantial shoulder at 940 nm. This suggests the presence of two charge transfer quenching sites in CP26 involving zeaxanthin radical cation and lutein radical cation species. We also show that lutein radical cation formation in CP26 is dependent on binding of zeaxanthin to the L2 domain, implying that zeaxanthin acts as an allosteric effector of charge transfer quenching involving lutein in the L1 domain.
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Department of Plant and Microbial Biology, Koshland Hall, University of California, Berkeley, California 94720-3102.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Avenson
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Ahn
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Department of Plant and Microbial Biology, Koshland Hall, University of California, Berkeley, California 94720-3102.
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
authors.affiliation: Department of Science and Technology, University of Verona, 37134 Verona, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Ballottari
authors.affiliation: Department of Science and Technology, University of Verona, 37134 Verona, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720. Electronic address: GRFleming@lbl.gov.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000187:drug effects* / Q000378:metabolism; D002412:Cations; D061146:Chlorophyll Binding Proteins; D002851:Chromatography, High Pressure Liquid; D045342:Light-Harvesting Protein Complexes / Q000187:drug effects* / Q000378:metabolism; D014975:Lutein / Q000494:pharmacology*; D045332:Photosystem II Protein Complex / Q000187:drug effects* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002412:Cations; D061146:Chlorophyll Binding Proteins; C490432:LHCB5 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D014975:Lutein