Determination of H+/ATP stoichiometry for the plasma membrane H+-ATPase from red beet (Beta vulgaris L.) storage tissue

Donald P. Briskin, Ingrid Reynolds-Niesman

Research output: Contribution to journalArticle

Abstract

The H+/ATP stoichiometry was determined for the plasma membrane H+-ATPaSe from red beet (Beta vulgaris L., var Detroit Dark Red) storage tissue associated with native vesicles. The determination of H+/ATP stoichiometry utilized a kinetic approach where rates of H+ influx, estimated by three different methods, were compared to rates of ATP hydrolysis measured by the coupled enzyme assay under identical conditions. These methods for estimating H+ influx were based upon either determining the initial rate of alkalinization of the external medium from pH 6.13, measuring the rate of vesicle H+ leakage from a steady-state pH gradient after stopping the H+-ATPase or utilizing a mathematical model which describes the net transport of H+ at any given point in time. When the rate of H+ influx estimated by each of these methods was compared to the rate of ATP hydrolysis, a H+/ATP stoichiometry of about 1 was observed. In consideration of the maximum free energy available from ATP hydrolysis (ΔGATP), this value for H+/ATP stoichiometry is sufficient to account for the magnitude of the proton electrochemical gradient observed across the plasma membrane in vivo.

Original languageEnglish (US)
Pages (from-to)242-250
Number of pages9
JournalPlant physiology
Volume95
Issue number1
DOIs
StatePublished - Jan 1991

ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Plant Science

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