Proton release upon oxidation of tyrosine in reaction centers from Rhodobacter sphaeroides

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8 Scopus citations


Markedly different light-induced protonational changes were measured in two reaction center mutants of Rhodobacter sphaeroides. A quadruple mutant containing alterations, at residues L131, M160, M197, and M210, that elevate the midpoint potential of the bacteriochlorophyll dimer was compared to the YM mutant, which contains these alterations plus a tyrosine at M164 serving as a secondary electron donor [Kálmán et al., Nature 402 (1999) 696]. In the quadruple mutant, a proton uptake of 0.1-0.3 H+/reaction center between pH 6 and 10 resulted from formation of the oxidized bacteriochlorophyll donor and reduced primary quinone. In the YM mutant, a maximal proton release of -0.5 H+/reaction center at pH 8 was attributed to formation of the tyrosyl radical and modeled using electrostatic and direct proton-releasing mechanisms.

Original languageEnglish (US)
Pages (from-to)193-198
Number of pages6
JournalFEBS Letters
Issue number2-3
StatePublished - Jun 19 2003


  • Amino acid radical
  • Electron transfer
  • Photosynthesis
  • Photosystem II
  • Proton transfer

ASJC Scopus subject areas

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


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