title: Low pH modulates the macroorganization and thermal stability of PSII supercomplexes in grana membranes.
abstract: Protonation of the lumen-exposed residues of some photosynthetic complexes in the grana membranes occurs under conditions of high light intensity and triggers a major photoprotection mechanism known as energy dependent nonphotochemical quenching. We have studied the role of protonation in the structural reorganization and thermal stability of isolated grana membranes. The macroorganization of granal membrane fragments in protonated and partly deprotonated state has been mapped by means of atomic force microscopy. The protonation of the photosynthetic complexes has been found to induce large-scale structural remodeling of grana membranes-formation of extensive domains of the major light-harvesting complex of photosystem II and clustering of trimmed photosystem II supercomplexes, thinning of the membrane, and reduction of its size. These events are accompanied by pronounced thermal destabilization of the photosynthetic complexes, as evidenced by circular dichroism spectroscopy and differential scanning calorimetry. Our data reveal a detailed nanoscopic picture of the initial steps of nonphotochemical quenching.
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Svetozar
authors.initials: S
authors.lastname: Stoichev
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Sashka B
authors.initials: SB
authors.lastname: Krumova
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Tonya
authors.initials: T
authors.lastname: Andreeva
authors.affiliation: Unidad de Biofísica (CSIC, UPV-EHU) and Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain.
authors.forename: Jon V
authors.initials: JV
authors.lastname: Busto
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Svetla
authors.initials: S
authors.lastname: Todinova
authors.affiliation: Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, Sofia University "St. Kliment Ohridski," Sofia, Bulgaria.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Balashev
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Mira
authors.initials: M
authors.lastname: Busheva
authors.affiliation: Unidad de Biofísica (CSIC, UPV-EHU) and Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain.
authors.forename: Félix M
authors.initials: FM
authors.lastname: Goñi
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria; Unidad de Biofísica (CSIC, UPV-EHU) and Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain. Electronic address: stefka.germanova@ehu.es.
authors.forename: Stefka G
authors.initials: SG
authors.lastname: Taneva
mesh_terms: D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D018532:Pisum sativum / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011489:Protein Denaturation; D020524:Thylakoids / Q000737:chemistry* / Q000201:enzymology
chemical_list: D045332:Photosystem II Protein Complex