Evidence that cytochrome b 559} is involved in superoxide production in photosystem II: effect of synthetic short-chain plastoquinones in a cytochrome b 559} tobacco mutant

Pavel Pospísil , Iva Snyrychová , Jerzy Kruk , Kazimierz Strzalka , Jan Naus , Pavel Pospísil (1)

1 Laboratory of Biophysics, Department of Experimental Physics

Light-induced production of superoxide (Osub2} ·-}) in spinach PSII membrane particles was studied using EPR spin-trapping spectroscopy. The presence of exogenous plastoquinones with a different side chain length enhanced O 2} ·-} production in the following order: PQ-1>PQ-2>>PQ-9. In PSII membrane particles isolated from tobacco mutant of cytochrome b 559} (cyt b 559}) carrying single-point mutation in the {beta}-subunit, which has also reduced amount of the {alpha}-subunit, the effect of PQ-1 was smaller than in the wild type. The increase in LP cyt b 559} content, induced by incubation of spinach PSII membrane particles at low pH, resulted in a significant increase in O 2} ·-} formation in the presence of PQ-1, whereas it had little effect on O 2} ·-} production in the absence of PQ-1. The enhancement of O 2} ·-} formation induced by PQ-1 was not abolished by DCMU. Under anaerobic conditions, dark oxidation of LP cyt b 559} increased as pH was decreased. The presence of molecular oxygen significantly enhanced dark oxidation of LP cyt b 559}. Based on these findings it is suggested that short-chain plastoquinones stimulate O 2} ·-} production via mechanism that involves electron transfer from Pheo -} to LP cyt b 559} and subsequent autooxidation of LP cyt b 559}.

Mots clés: Life Sciences

Pavel Pospísil, Iva Snyrychová, Jerzy Kruk, Kazimierz Strzalka, Jan Naus, et al.. Evidence that cytochrome b 559} is involved in superoxide production in photosystem II: effect of synthetic short-chain plastoquinones in a cytochrome b 559} tobacco mutant. Biochemical Journal, 2006, 397 (2), pp.321-327. ⟨10.1042/BJ20060068⟩. ⟨hal-00478511⟩