title: Pigment interactions in light-harvesting complex II in different molecular environments.
abstract: Extraction of plant light-harvesting complex II (LHCII) from the native thylakoid membrane or from aggregates by the use of surfactants brings about significant changes in the excitonic circular dichroism (CD) spectrum and fluorescence quantum yield. To elucidate the cause of these changes, e.g. trimer-trimer contacts or surfactant-induced structural perturbations, we compared the CD spectra and fluorescence kinetics of LHCII aggregates, artificial and native LHCII-lipid membranes, and LHCII solubilized in different detergents or trapped in polymer gel. By this means we were able to identify CD spectral changes specific to LHCII-LHCII interactions, at (-)-437 and (+)-484 nm, and changes specific to the interaction with the detergent n-dodecyl-β-maltoside (β-DM) or membrane lipids, at (+)-447 and (-)-494 nm. The latter change is attributed to the conformational change of the LHCII-bound carotenoid neoxanthin, by analyzing the CD spectra of neoxanthin-deficient plant thylakoid membranes. The neoxanthin-specific band at (-)-494 nm was not pronounced in LHCII in detergent-free gels or solubilized in the α isomer of DM but was present when LHCII was reconstituted in membranes composed of phosphatidylcholine or plant thylakoid lipids, indicating that the conformation of neoxanthin is sensitive to the molecular environment. Neither the aggregation-specific CD bands, nor the surfactant-specific bands were positively associated with the onset of fluorescence quenching, which could be triggered without invoking such spectral changes. Significant quenching was not active in reconstituted LHCII proteoliposomes, whereas a high degree of energetic connectivity, depending on the lipid:protein ratio, in these membranes allows for efficient light harvesting.
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, 6726 Szeged and.
authors.forename: Parveen
authors.initials: P
authors.lastname: Akhtar
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, 6726 Szeged and.
authors.forename: Márta
authors.initials: M
authors.lastname: Dorogi
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, 6726 Szeged and.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Pawlak
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, 6726 Szeged and.
authors.forename: László
authors.initials: L
authors.lastname: Kovács
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, 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, Biological Research Centre, Temesvári krt. 62, 6726 Szeged and.
authors.forename: Győző
authors.initials: G
authors.lastname: Garab
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, 6726 Szeged and. Electronic address: lambrev@brc.hu.
authors.forename: Petar H
authors.initials: PH
authors.lastname: Lambrev
mesh_terms: D002942:Circular Dichroism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D018532:Pisum sativum / Q000201:enzymology*; D020524:Thylakoids / Q000201:enzymology*; D024341:Xanthophylls / Q000737:chemistry*
chemical_list: D045342:Light-Harvesting Protein Complexes; D008563:Membrane Lipids; D024341:Xanthophylls; C011947:neoxanthin
keywords: Circular Dichroism (CD); Conformational Change; Detergent Solubilization; Fluorescence; Membrane Protein; Non-photochemical Quenching; Photosynthetic Pigment; Protein Aggregation