Quantitation of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone binding sites in chloroplast membranes: Evidence for a functional dimer of the cytochrome b6f complex

Thomas Graan, Donald R. Ort

Research output: Contribution to journalArticlepeer-review

Abstract

The binding of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) to chloroplast thylakoid membranes was investigated by analyzing the inhibition of electron transfer by DBMIB according to a steady-state rate relationship for enzyme-catalyzed reactions in the presence of tightly binding reversible inhibitors. DBMIB interacts with the cytochrome b6f complex in a manner best described by an apparent dissociation constant near 6 nm. The binding site titer is 1 mmol · mol chlorophyll-1. This number of DBMIB binding sites approaches one-half the number of cytochrome b6f complexes present in the membrane. These data suggest that the cytochrome b6f complex may function in electron transfer as a dimer, plastoquinol oxidation being totally inhibited by the binding of a single DBMIB molecule to the dimer.

Original languageEnglish (US)
Pages (from-to)445-451
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume248
Issue number2
DOIs
StatePublished - Aug 1 1986
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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