PKa of the essential Glu54 and backbone conformation for subunit c from the H+-coupled F1F0 ATP synthase from an alkaliphilic Bacillus

Iván O. Rivera-Torres, Ray D. Krueger-Koplin, David B. Hicks, Sean M. Cahill, Terry A. Krulwich, Mark E. Girvin

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8 Scopus citations


The conformation of the ATP synthase c-subunit and the pKa of its essential E54 residue were characterized in alkaliphilic Bacillus pseudofirmus OF4. The c-subunit folds as a helix-loop-helix, with inter-helical contacts demonstrated by paramagnetic relaxation effects. The E54 pKa of 7.7 is significantly higher than in non-alkaliphiles, which likely prevents proton loss from the c-rotor at high pH. The E54 pKa was unchanged in a mutant, cP51A, that has a severe ATP synthesis defect at high pH only. cP51 must have some structural role that accounts for the mutant defect, such as different subunit-subunit interactions at high pH.

Original languageEnglish (US)
Pages (from-to)131-135
Number of pages5
JournalFEBS Letters
Issue number1-3
StatePublished - Sep 24 2004


  • Alkaliphile
  • Membrane protein
  • NMR
  • Oxidative phosphorylation

ASJC Scopus subject areas

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


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