pH dependent inactivation of solubilized F1F0 ATP synthase by dicyclohexylcarbodiimide: pKa of detergent unmasked aspartyl-61 in Escherichia coli subunit c

Francis Valiyaveetil, Joe Hermolin, Robert H. Fillingame

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


The pH dependence of the reaction of dicyclohexylcarbodiimide with the essential aspartyl-61 residue in subunit c of Escherichia coli ATP synthase was compared in membranes and in a detergent dispersed preparation of the enzyme. The rate of reaction was estimated by measuring the inactivation of ATPase activity. The reaction with the detergent dispersed form of the enzyme proved to be pH sensitive with the essential aspartyl group titrating with a pKa = 8. However, when measured with E. coli membranes, the reaction proved to be pH insensitive. The results suggest that the reacting aspartyl-61 residues are shielded from the bulk aqueous solvent when in the membrane, but then become aqueous-accessible following detergent solubilization.

Original languageEnglish (US)
Pages (from-to)296-301
Number of pages6
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number3
StatePublished - Feb 15 2002
Externally publishedYes


  • ATP synthase
  • ATPase inhibition
  • Dicyclohexylcarbodiimide
  • Essential carboxyl
  • Proton transport
  • Subunit c
  • pH dependence

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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