title: Period-four modulation of photosystem II primary quinone acceptor (Q(A)) reduction/oxidation kinetics in thylakoid membranes.
abstract: Photosystem II (PSII), a multiprotein complex mainly coded by the chloroplast genome in higher plants and algae, contains the oxygen-evolving complex with four manganese atoms responsible for the oxidation of water. After each absorption of a light quantum by pigment molecules in the light harvesting complexes of PSII, the Mn cluster advances in its oxidation states denoted from S(0) to S(4) . The S(4) state decays to S(0) in the dark with the concurrent release of molecular oxygen. Therefore, the oxygen production in PSII exposed to successive single turnover excitations follows a period-four oscillation pattern. The intensity of chlorophyll a fluorescence of PSII is also known to be influenced by the oxidation state of the Mn cluster. In the present work, fluorescence induction kinetics was measured in isolated thylakoids with various initial S-state populations settled by preflashes. The shape of the fluorescence induction traces was strongly affected by preflashes. O-J and J-I phases of the induction followed a period-four oscillation pattern. The results indicate that these changes reflect the influence of the oxidation rate of the Mn cluster on the reduction/oxidation kinetics of the primary quinone acceptor (Q(A) ) of PSII.
authors.affiliation: Groupe de Recherche en Biologie Végétale (GRBV), Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada.
authors.forename: Alain
authors.initials: A
authors.lastname: Gauthier
authors.forename: David
authors.initials: D
authors.lastname: Joly
authors.forename: Steve
authors.initials: S
authors.lastname: Boisvert
authors.forename: Robert
authors.initials: R
authors.lastname: Carpentier
mesh_terms: D007700:Kinetics; D008345:Manganese / Q000737:chemistry; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011809:Quinones / Q000737:chemistry*; D020524:Thylakoids / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D045332:Photosystem II Protein Complex; D011809:Quinones; D014867:Water; D008345:Manganese