title: Excitation energy transfer between Light-harvesting complex II and Photosystem I in reconstituted membranes.
abstract: Light-harvesting complex II (LHCII), the major peripheral antenna of Photosystem II in plants, participates in several concerted mechanisms for regulation of the excitation energy and electron fluxes in thylakoid membranes. In part, these include interaction of LHCII with Photosystem I (PSI) enhancing the latter's absorption cross-section - for example in the well-known state 1 - state 2 transitions or as a long-term acclimation to high light. In this work we examined the capability of LHCII to deliver excitations to PSI in reconstituted membranes in vitro. Proteoliposomes with native plant thylakoid membrane lipids and different stoichiometric ratios of LHCII:PSI were reconstituted and studied by steady-state and time-resolved fluorescence spectroscopy. Fluorescence emission from LHCII was strongly decreased in PSI-LHCII membranes due to trapping of excitations by PSI. Kinetic modelling of the time-resolved fluorescence data revealed the existence of separate pools of LHCII distinguished by the time scale of energy transfer. A strongly coupled pool, equivalent to one LHCII trimer per PSI, transferred excitations to PSI with near-unity efficiency on a time scale of less than 10ps but extra LHCIIs also contributed significantly to the effective antenna size of PSI, which could be increased by up to 47% in membranes containing 3 LHCII trimers per PSI. The results demonstrate a remarkable competence of LHCII to increase the absorption cross-section of PSI, given the opportunity that the two types of complexes interact in the membrane.
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Institute of Plant Biology, Temesvári krt. 62, 6726 Szeged, Hungary.
authors.forename: Parveen
authors.initials: P
authors.lastname: Akhtar
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Institute of Plant Biology, Temesvári krt. 62, 6726 Szeged, Hungary.
authors.forename: Mónika
authors.initials: M
authors.lastname: Lingvay
authors.affiliation: Hungarian Academy of Sciences, Research Centre for Natural Sciences, Institute of Materials and Environmental Chemistry, Magyar tudósok körútja 2, 1117 Budapest, Hungary.
authors.forename: Teréz
authors.initials: T
authors.lastname: Kiss
authors.affiliation: Hungarian Academy of Sciences, Research Centre for Natural Sciences, Institute of Materials and Environmental Chemistry, Magyar tudósok körútja 2, 1117 Budapest, Hungary.
authors.forename: Róbert
authors.initials: R
authors.lastname: Deák
authors.affiliation: Hungarian Academy of Sciences, Research Centre for Natural Sciences, Institute of Materials and Environmental Chemistry, Magyar tudósok körútja 2, 1117 Budapest, Hungary.
authors.forename: Attila
authors.initials: A
authors.lastname: Bóta
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Institute of Plant Biology, Temesvári krt. 62, 6726 Szeged, Hungary; ELI-ALPS, ELI-HU Non-Profit Ltd., Dugonics tér 13, 6720 Szeged, Hungary.
authors.forename: Bettina
authors.initials: B
authors.lastname: Ughy
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Institute of Plant Biology, Temesvári krt. 62, 6726 Szeged, Hungary.
authors.forename: Győző
authors.initials: G
authors.lastname: Garab
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Institute of Plant Biology, Temesvári krt. 62, 6726 Szeged, Hungary. Electronic address: lambrev.petar@brc.mta.hu.
authors.forename: Petar H
authors.initials: PH
authors.lastname: Lambrev
mesh_terms: D002942:Circular Dichroism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D011510:Proteolipids / Q000737:chemistry
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D011510:Proteolipids; C020485:proteoliposomes
keywords: Artificial membranes; Light harvesting; Proteoliposomes; State transitions; Thylakoid membranes; Time-resolved fluorescence