title: Heat- and light-induced detachment of the light-harvesting antenna complexes of photosystem I in isolated stroma thylakoid membranes.
abstract: The multisubunit pigment-protein complex of photosystem I (PSI) consists of a core and peripheral light-harvesting antenna (LHCI). PSI is thought to be a rather rigid system and very little is known about its structural and functional flexibility. Recent data, however, suggest LHCI detachment from the PSI supercomplex upon heat and light treatments. Furthermore, it was suggested that the splitting off of LHCI acts as a safety valve for PSI core upon photoinhibition (Alboresi et al., 2009). In this work we analyzed the heat- and light-induced reorganizations in isolated PSI vesicles (stroma membrane vesicles enriched in PSI). Using differential scanning calorimetry we revealed a stepwise disassembly of PSI supercomplex above 50°C. Circular dichroism, sucrose gradient centrifugation and 77K fluorescence experiments identified the sequence of events of PSI destabilization: 3min heating at 60°C or 40min white light illumination at 25°C resulted in pronounced Lhca1/4 detachment from the PSI supercomplex, which is then followed by the degradation of Lhca2/3. The similarity of the main structural effects due to heat and light treatments supports the notion that thermo-optic mechanism, structural changes induced by ultrafast local thermal transients, which has earlier been shown to be responsible for structural changes in the antenna system of photosystem II, can also regulate the assembly and functioning of PSI antenna.
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary.
authors.forename: S B
authors.initials: SB
authors.lastname: Krumova
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary.
authors.forename: Zs
authors.initials: Z
authors.lastname: Várkonyi
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary.
authors.forename: P H
authors.initials: PH
authors.lastname: Lambrev
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary.
authors.forename: L
authors.initials: L
authors.lastname: Kovács
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Bl. 21, 1113 Sofia, Bulgaria.
authors.forename: S J
authors.initials: SJ
authors.lastname: Todinova
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Bl. 21, 1113 Sofia, Bulgaria.
authors.forename: M C
authors.initials: MC
authors.lastname: Busheva
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Bl. 21, 1113 Sofia, Bulgaria.
authors.forename: S G
authors.initials: SG
authors.lastname: Taneva
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary. Electronic address: garab.gyozo@brc.mta.hu.
authors.forename: G
authors.initials: G
authors.lastname: Garab
mesh_terms: D004795:Enzyme Stability / Q000528:radiation effects; D006358:Hot Temperature; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D018724:Spinacia oleracea / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects; D020524:Thylakoids / Q000201:enzymology* / Q000528:radiation effects*; D013997:Time Factors
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex