Flash-induced reduction of cytochrome b-559 by QinfBsup- in chloroplasts in the presence of protonophores

Klára Barabás, Tatjana Kravcova, Gyozo Garab

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Abstract

Flash-induced, fast (t1/2 ≈ 1 ms), reversible reduction of the high potential cytochrome b-559 (cyt b-559HP) was observed in chloroplasts in the presence of 2 μM protonophore, FCCP (carbonylcyanide p-trifluoromethoxyphenylhydrazone), CCCP (carbonylcyanide 3-chlorophenylhydrazone) or SF 6847 (2,6-di-(t-butyl)-4-(2′,2′-dicyanovinyl)phenol). These protonophores promote autooxidation of cyt b-559HP in the dark (Arnon and Tang 1988, Proc Natl Acad Sci USA 85: 9524). No fast photoreduction could, however, be observed if the molecules were oxidized with ferricyanide in the absence of protonophores. This suggests that the molecules must be deprotonated to be capable for fast photoreduction. Photoreduction of cyt b-559HP was largely insensitive to DBMIB (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone), but was inhibited by DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea). With a train of flashes, no oscillation could be observed in the amplitudes of photoreduction. These data strongly suggest that cyt b-559HP is reduced by the semireduced secondary quinone acceptor (QB-) of Photosystem 2.

Original languageEnglish
Pages (from-to)59-64
Number of pages6
JournalPhotosynthesis research
Volume36
Issue number1
DOIs
Publication statusPublished - Apr 1 1993

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Keywords

  • ADRY
  • Photosystem 2
  • deprotonation
  • high potential form of cytochrome b-559
  • photoreduction

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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