Cadmium transport across tonoplast of vesicles from oat roots: Evidence for a Cd2+/H+ antiport activity

D E Salt, G J Wagner

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Abstract

Cadmium accumulates in the vacuole of plant cells, but the mechanism driving its transport across the vacuole membrane is not understood. Here we present evidence for Cd2+ transport via a Cd2+/H+ antiport activity into tonoplast-enriched vesicles isolated from oat roots. Experimentally, accumulation of Cd2+ into vesicles could be driven by DELTApH generated by either V-type ATPase or artificially using nigericin to exchange K+ and H+ in K+-loaded vesicles. When tonoplast-enriched vesicles were separated on a linear sucrose gradient, NO3--sensitive ATPase, total MgATPase, and DELTApH-dependent Cd2+ transport equilibrated at 1.11 g/ml, the density of tonoplast membrane. Cd2+ accumulation in vesicles was accompanied by efflux of protons in a Cd2+ concentration-dependent manner characteristic of an antiport activity. The DELTApH-dependent Cd2+ accumulation process showed saturation kinetics with a K(m(app)) of 5.5 muM. Thus the process is a candidate for transport of Cd2+ from the cytoplasm to the vacuolar sap under conditions of low as well as high Cd2+ exposure.

Original languageEnglish
Pages (from-to)12297-12302
Number of pages6
JournalThe Journal of Biological Chemistry
Volume268
Issue number17
Publication statusPublished - 15 Jun 1993

Keywords

  • H+-pumping atpase
  • beta-vulgaris L
  • membrane-vesicles
  • calcium-transport
  • CA2+/H+ antiport
  • suspension cells
  • acridine-orange
  • system driven
  • binding
  • tobacco

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