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Inhibition of the glucose and amino‐acid carriers of Lemna gibba by pretreatment with HgCl 2
Author(s) -
Golle Bernd,
Lüttge Ulrich
Publication year - 1983
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1983.tb00730.x
Subject(s) - lemna gibba , chemistry , membrane potential , cotransporter , salicylhydroxamic acid , lemna , dithiothreitol , biochemistry , stereochemistry , biophysics , botany , organic chemistry , biology , sodium , enzyme , macrophyte , ecology , aquatic plant
The electrical resting potential across the plasmalemma of Lemna gibba L. (G 1) cells is −230 to −250 mV and the diffusion potential in the presence of 1 mol m −3 KCN + 1 mol m −3 salicylhydroxamic acid is about −100 mV. A concentration of 0.01 mol m −3 HgCl 2 depolarises the transmembrane electrical potential in a largely reversible way. When the cells after 16 min of HgCl 2 ‐application are returned to Hg‐free solution, the transmembrane electrical potential is only depolarised by 24 × 13 mV (SD, n = 13) compared with the potential prior to HgCl 2 treatment. In contrast, a 16 min pretreatment with HgCl 2 followed by a wash with mercury‐free solution reduces the transient depolarisations of transmembrane potential observed after addition of 5 mol m −3 D‐glncose or 1 mol m −3 L‐alaoine to about 60% of controls. These transient depolarisations are due to the onset of solute uptake. Accordingly, HgCl 2 ‐pretreatment inhibits uptake of 14 C‐3‐O‐methyl‐ d ‐glucose by more than 50% and uptake of 14 C‐ l ‐alanine by more than 70%. Washing with 1 mol m −3 1,4‐dithiothreitol does not reverse this inhibition. It is, therefore, concluded that Hg 2+ irreversibly binds to essential SH‐groups of the H + ‐hexose and the H + ‐amino‐acid cotransport carriers of Lemna gibba and inhibits these carriers without appreciably affecting the electrogenic proton‐extrusion pump.