Characterization of a Light-modulated ATPase Activity in a Microsomal Fraction from Cucumber Hypocotyls

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The properties of ATPase activity in a microsomal fraction from etiolated hypocotyls of Cucumis sativus L. were investigated. The ATPase required Mg2+, was stimulated by K+ and was partially inhibited by vanadate. The effect of K+ was unspecific and suggested that, at the tested concentration (50 mM), K+ stimulated ATPase activity by facilitating H+ extrusion by the ATPase and in turn its further activity. This assumption was supported by the effect of the K+ and pH gradients on K+ stimulation. The stimulation by K+ was increased by red light treatments, while red irradiation in vivo followed by far red irradiation in vitro was less stimulatory. This implies that phytochrome modulates the K+ stimulation. Ionophores such as gramicidin and nigericin also stimulated the ATPase activity in the presence of K+. This effect was prominent only after far red irradiation in vitro.

Original languageEnglish
Pages (from-to)315-327
Number of pages13
JournalJournal of Plant Physiology
Issue number4
StatePublished - 1 Jan 1986
Externally publishedYes


  • 2-(N-morpholino)ethanesulphonic acid
  • ATPase
  • Cucumis sativus
  • DTT
  • EGTA
  • MES
  • Pfr
  • Pr
  • dithiothreitol
  • ethyleneglycoltetraacetic acid
  • far red absorbing form of phytochrome
  • ionopbores
  • phytochrome
  • potassium
  • red absorbing form of phytochrome
  • vanadate

ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science
  • Plant Science


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