Author(s): Salt DE, Wagner GJ
Abstract Share this page
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 delta pH 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 delta pH-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 delta pH-dependent Cd2+ accumulation process showed saturation kinetics with a Km(app) of 5.5 microM. 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.
This article was published in J Biol Chem
and referenced in Biochemistry & Pharmacology: Open Access