title: Dynamics of zeaxanthin binding to the photosystem II monomeric antenna protein Lhcb6 (CP24) and modulation of its photoprotection properties.
abstract: Lhcb6 (CP24) is a monomeric antenna protein of photosystem II, which has been shown to play special roles in photoprotective mechanisms, such as the Non-Photochemical Quenching and reorganization of grana membranes in excess light conditions. In this work we analyzed Lhcb6 in vivo and in vitro: we show this protein, upon activation of the xanthophyll cycle, accumulates zeaxanthin into inner binding sites faster and to a larger extent than any other pigment-protein complex. By comparative analysis of Lhcb6 complexes violaxanthin or zeaxanthin binding, we demonstrate that zeaxanthin not only down-regulates chlorophyll singlet excited states, but also increases the efficiency of chlorophyll triplet quenching, with consequent reduction of singlet oxygen production and significant enhancement of photo-stability. On these bases we propose that Lhcb6, the most recent addition to the Lhcb protein family which evolved concomitantly to the adaptation of photosynthesis to land environment, has a crucial role in zeaxanthin-dependent photoprotection.
authors.affiliation: Dipartimento di Biotecnologie, Università di Verona, Ca' Vignal 1, Strada le Grazie 15, I-37134 Verona, Italy.
authors.forename: Nico
authors.initials: N
authors.lastname: Betterle
authors.forename: Matteo
authors.initials: M
authors.lastname: Ballottari
authors.forename: Rainer
authors.initials: R
authors.lastname: Hienerwadel
authors.forename: Luca
authors.initials: L
authors.lastname: Dall'Osto
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D061146:Chlorophyll Binding Proteins; D004852:Epoxy Compounds / Q000737:chemistry; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D038761:Photobleaching; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D011485:Protein Binding; D026082:Singlet Oxygen / Q000378:metabolism; D013057:Spectrum Analysis; D020524:Thylakoids / Q000378:metabolism; D024341:Xanthophylls / Q000737:chemistry / Q000378:metabolism*; D065146:Zeaxanthins
chemical_list: D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; D004852:Epoxy Compounds; C490432:LHCB5 protein, Arabidopsis; C529795:Lhcb6 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D065146:Zeaxanthins; D002734:Chlorophyll; D026082:Singlet Oxygen; C005613:violaxanthin