The redox potential of the primary quinone QA of bacterial photosynthesis is independent of the divalent metal ion

Susan K. Buchanan, G. Charles Dismukes, Roger C. Prince

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


The function of the ferrous ion which links the primary and secondary quinone electron acceptors, QA and QB, via histidine ligands from the reaction center protein of the photosynthetic bacterium Rbodobacter sphaeroids (Y) has been investigated by substitution with Mn(II), Cu(II) and Zn(II), using biosynthetic incorporation of the metal ion. The midpoint potential and pH dependence for reduction of QA in chromatophore membranes were found to be indistinguishable for all four divalent ions, and in agreement with earlier results on the R26 and Ga strains of R. sphaeroides containing only iron. We therefore conclude that the divalent ion contributes no functionally significant covalent coupling to the primary acceptor and that these metals have no differential electrostatic influence. Furthermore, inhibition of photoreduction of QB by the herbicide ametryne was found to be the same for all four samples. Thus, these four divalent ions exhibit no differential influence on the binding properties of this herbicide in the QB site.

Original languageEnglish
Pages (from-to)16-20
Number of pages5
JournalFEBS Letters
Issue number1
Publication statusPublished - Feb 29 1988


  • Bacterial photosynthesis
  • Electron transport
  • Metal substitution
  • Reaction center
  • Ubiquinone

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

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