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 journalArticle

20 Citations (Scopus)

Abstract

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
Volume1553
Issue number3
DOIs
StatePublished - Feb 15 2002
Externally publishedYes

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Dicyclohexylcarbodiimide
Detergents
Escherichia coli
Membranes
Enzymes
Adenosine Triphosphatases
Adenosine Triphosphate
F1F0-ATP synthase

Keywords

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

ASJC Scopus subject areas

  • Biophysics

Cite this

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title = "pH dependent inactivation of solubilized F1F0 ATP synthase by dicyclohexylcarbodiimide: pKa of detergent unmasked aspartyl-61 in Escherichia coli subunit c",
abstract = "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.",
keywords = "ATP synthase, ATPase inhibition, Dicyclohexylcarbodiimide, Essential carboxyl, pH dependence, Proton transport, Subunit c",
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T1 - pH dependent inactivation of solubilized F1F0 ATP synthase by dicyclohexylcarbodiimide

T2 - pKa of detergent unmasked aspartyl-61 in Escherichia coli subunit c

AU - Valiyaveetil, Francis

AU - Hermolin, Joe

AU - Fillingame, Robert H.

PY - 2002/2/15

Y1 - 2002/2/15

N2 - 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.

AB - 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.

KW - ATP synthase

KW - ATPase inhibition

KW - Dicyclohexylcarbodiimide

KW - Essential carboxyl

KW - pH dependence

KW - Proton transport

KW - Subunit c

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