Cadmium transport across tonoplast of vesicles from oat roots

Evidence for a Cd2+/H+ antiport activity

D E Salt, G J Wagner

Research output: Contribution to journalArticle

162 Citations (Scopus)

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

Cite this

Cadmium transport across tonoplast of vesicles from oat roots : Evidence for a Cd2+/H+ antiport activity. / Salt, D E ; Wagner, G J .

In: The Journal of Biological Chemistry, Vol. 268, No. 17, 15.06.1993, p. 12297-12302.

Research output: Contribution to journalArticle

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AU - Wagner, G J

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N2 - 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.

AB - 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.

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KW - calcium-transport

KW - CA2+/H+ antiport

KW - suspension cells

KW - acridine-orange

KW - system driven

KW - binding

KW - tobacco

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JO - The Journal of Biological Chemistry

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