Vacuolar uptake of the phytoalexin medicarpin by the glutathione conjugate pump.
We have studied the uptake of [3H]-medicarpin and its glutathione conjugate(s) into vacuolar membrane vesicles from etiolated hypocotyls of mung bean (Vigna radiata). Unconjugated medicarpin is taken up at a low rate in the presence or absence of MgATP. However, [3H]-medicarpin-glutathione conjugate(s), prepared by incubation of medicarpin with a total maize glutathione S-transferase preparation, is taken up more than four-fold faster than medicarpin in the presence of MgATP, and this uptake is MgATP-dependent. Uptake of medicarpin-glutathione was not significantly inhibited by the ionophore gramicidin-D, but was strongly inhibited by vanadate and the alternative transport substrate S-(2,4-dinitrophenyl) glutathione. Our results demonstrate, in a model system, the potential utilization of the high affinity, high capacity, uncoupler-insensitive glutathione conjugate pump for the vacuolar transport of an isoflavonoid phytoalexin.
Li
Z S
ZS
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
Alfenito
M
M
Rea
P A
PA
Walbot
V
V
Dixon
R A
RA
D000255:Adenosine Triphosphate / Q000494:pharmacology; D001578:Benzopyrans / Q000378:metabolism*; D007887:Fabaceae / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D010946:Plants, Medicinal; D036343:Pterocarpans; D014316:Tritium; D014617:Vacuoles / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology; D000094162:Phytoalexins
D000255:Adenosine Triphosphate; D001578:Benzopyrans; D005978:Glutathione; D005982:Glutathione Transferase; D036343:Pterocarpans; D014316:Tritium; C047353:medicarpin; D000094162:Phytoalexins