Small pH Gradients inhibit cytochrome C oxidase: Implications for H+ entry to the binuclear center

Martyn A. Sharpe, John M. Wrigglesworth, Jerome Loewen, Peter Nicholls

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Respiring cytochrome c oxidase proteoliposomes generate internal alkalinity (ΔpH) and a membrane potential (ΔΨ). Valinomycin collapses ΔΨ, increases ΔpH, and slows steady state respiration. If ΔpH is heterogeneously expressed trapped probes will underestimate it. Internal pH changes were therefore followed in COV containing two buffer systems of differing pKs. The alkalinization rate at pH 7 was unaffected by adding AMPSO (pK 9.0) to the usual internal HEPES (pK 7.5). At higher pH, AMPSO slowed the approach to steady state. ΔpH inhibition is therefore not due to a large alkalinization in a small COV fraction. The O2-reducing center may move protons via a local aqueous phase that is near electrical and pH equilibrium with the phase inside the COV. The dielectric in this membrane region can put the center electrically 'inside' even though it is physically 'outside'.

Original languageEnglish (US)
Pages (from-to)931-938
Number of pages8
JournalBiochemical and Biophysical Research Communications
Volume216
Issue number3
DOIs
StatePublished - 1995

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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