title: Spermine and spermidine inhibition of photosystem II: Disassembly of the oxygen evolving complex and consequent perturbation in electron donation from TyrZ to P680+ and the quinone acceptors QA- to QB.
abstract: Polyamines are implicated in plant growth and stress response. However, the polyamines spermine and spermidine were shown to elicit strong inhibitory effects in photosystem II (PSII) submembrane fractions. We have studied the mechanism of this inhibitory action in detail. The inhibition of electron transport in PSII submembrane fractions treated with millimolar concentrations of spermine or spermidine led to the decline of plastoquinone reduction, which was reversed by the artificial electron donor diphenylcarbazide. The above inhibition was due to the loss of the extrinsic polypeptides associated with the oxygen evolving complex. Thermoluminescence measurements revealed that charge recombination between the quinone acceptors of PSII, QA and QB, and the S2 state of the Mn-cluster was abolished. Also, the dark decay of chlorophyll fluorescence after a single turn-over white flash was greatly retarded indicating a slower rate of QA- reoxidation.
authors.affiliation: Groupe de recherche en Biologie Végétale, Université du Québec à Trois-Rivières, CP 500, Trois-Rivières (Québec), Canada G9A 5H7.
authors.forename: Rémy
authors.initials: R
authors.lastname: Beauchemin
authors.forename: Alain
authors.initials: A
authors.lastname: Gauthier
authors.forename: Johanne
authors.initials: J
authors.lastname: Harnois
authors.forename: Steve
authors.initials: S
authors.lastname: Boisvert
authors.forename: Sridharan
authors.initials: S
authors.lastname: Govindachary
authors.forename: Robert
authors.initials: R
authors.lastname: Carpentier
mesh_terms: D002734:Chlorophyll / Q000737:chemistry; D004579:Electron Transport; D004583:Electrons; D005453:Fluorescence; D008345:Manganese / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000037:antagonists & inhibitors* / Q000737:chemistry; D011809:Quinones / Q000737:chemistry*; D013095:Spermidine / Q000737:chemistry / Q000494:pharmacology*; D013096:Spermine / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D010455:Peptides; D045332:Photosystem II Protein Complex; D011809:Quinones; D002734:Chlorophyll; D013096:Spermine; D008345:Manganese; D010100:Oxygen; D013095:Spermidine