title: Energizing the light harvesting antenna: Insight from CP29.
abstract: How do plants cope with excess light energy? Crop health and stress tolerance are governed by molecular photoprotective mechanisms. Protective exciton quenching in plants is activated by membrane energization, via unclear conformational changes in proteins called antennas. Here we show that pH and salt gradients stimulate the response of such an antenna under low and high energization by all-atom Molecular Dynamics Simulations. Novel insight establishes that helix-5 (H5) conformation in CP29 from spinach is regulated by chemiosmotic factors. This is selectively correlated with the chl-614 macrocycle deformation and interactions with nearby pigments, that could suggest a role in plant photoprotection. Adding to the significance of our findings, H5 domain is conserved among five antennas (LHCB1-5). These results suggest that light harvesting complexes of Photosystem II, one of the most abundant proteins on earth, can sense chemiosmotic gradients via their H5 domains in an upgraded role from a solar detector to also a chemiosmotic sensor.
authors.affiliation: Department of Environmental Science & Technology, Cyprus University of Technology, P.O. Box 50329, Limassol, Cyprus. Electronic address: ioannidis@biology.uoc.gr.
authors.forename: Nikolaos E
authors.initials: NE
authors.lastname: Ioannidis
authors.affiliation: Department of Environmental Science & Technology, Cyprus University of Technology, P.O. Box 50329, Limassol, Cyprus.
authors.forename: Sotiris
authors.initials: S
authors.lastname: Papadatos
authors.affiliation: Department of Environmental Science & Technology, Cyprus University of Technology, P.O. Box 50329, Limassol, Cyprus. Electronic address: evangelos.daskalakis@cut.ac.cy.
authors.forename: Vangelis
authors.initials: V
authors.lastname: Daskalakis
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D045332:Photosystem II Protein Complex / Q000378:metabolism* / Q000502:physiology; D000072417:Protein Domains / Q000502:physiology; D018724:Spinacia oleracea / Q000378:metabolism / Q000502:physiology
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D002734:Chlorophyll
keywords: Antenna proteins; Non photochemical quenching; Photoprotection; Photosystem II; Proton motive force