Uni-site catalysis in thylakoids. The influence of membrane energization on ATP hydrolysis and ATP-Pi exchange

Petra Fromme, Peter Gräber

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

ATP-hydrolysis was measured with thylakoid membranes during continuous illumination. The concentrations of free and enzyme-bound ATP, ADP and Pi were measured using either cold ATP, [γ-32P]ATP or [14C]ATP. The concentration of free ATP was constant, free ADP and enzyme-bound ATP were below the detection limit. Nevertheless, [γ-32P]ATP was bound, hydrolyzed and 32Pi was released. The ADP was not released from the enzyme but cold Pi was bound from the medium, cold ATP was resynthesized and released. A quantitative analysis gave the following rate constants: ATP-binding kATP = 2·105 M-1s-1, ADP-release: kADP -2s-1, Pi-release: kPi = 0.1 s-1. These rate constants are considerably smaller than under deenergized conditions. The rate constant for the release of ATP can be estimated to be at least 0.2 s-1 under energized conditions. Obviously, energization of the membrane, i.e. protonation of the enzyme leads mainly to a decrease of the rate of ATP-binding, to an increase of the rate of ATP release and to a decrease of the rate of ADP-release.

Original languageEnglish
Pages (from-to)247-251
Number of pages5
JournalFEBS Letters
Volume269
Issue number1
DOIs
Publication statusPublished - Aug 20 1990

Keywords

  • ATP synthesis
  • ATP-P exchange
  • CFF
  • Chloroplast
  • H-ATPase
  • Uni-site catalysis

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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