Cd/H antiport

david salt BOTSALT at VM.UOGUELPH.CA
Fri Feb 19 00:11:13 EST 1993


This is the abstract I will be presenting at this years ASPP meeting.
I thought that I would post it to plant-biology to see if anybody has
any comments or suggestions.

CADMIUM TRANSPORT ACROSS TONOPLAST OF VESICLES FROM OAT ROOTS

David E. Salt1 and George J. Wagner2 1Botany Dept., Univ.
Guelph, Guelph, Ontario, Canada; 2Agronomy Dept., Univ.
Kentucky, Kentucky, USA.

Cadmium accumulates in the vacuole of plant cells(1, 2) but the
mechanism driving  its transport across the vacuole membrane is
not understood. We have demonstrated Cd2+ transport via a
Cd2+/H+ antiport activity into tonoplast-enriched vesicles
isolated from oat roots(3). Experimentally, accumulation of Cd2+
into vesicles could be driven by DpH 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   DpH 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 Cd-concentration-dependent manner characteristic of an
antiport activity. The DpH dependent Cd2+ accumulation process
showed saturation kinetics with a Km(app) of 5.5microM. 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.

1. Vogeli-Lange R., and Wagner G.J. (1990) Plant Physiol. 92,
1086-1093.
2. Krotz R.M., Evangelou B.P., and Wagner G.J. (1989) Plant
Physiol. 91, 780-787.
3. Salt D.E., and Wagner G.J. (1993) J. Biol. Chem. in press.

See you in Minneapolis

David Salt



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