Cotransport of phosphate and sodium by yeast

Relationship between Energy-dependent Phosphate Uptake and the Electrical Membrane Potential in Lemna gibba G1

“…In plants maintaining a low pd (-110 Phosphate uptake by unicellular algae is stimulated up to 10-fold by Na+ or Li' ions in the neutral and alkaline pH range (23,24). The same was found in fungi (18,19) and was interpreted as a Na+-phosphate co-transport system (18). In addition, it has been shown in yeast and in bacteria that, in the acidic pH range, phosphate absorption is accompanied by an H+ influx with a stoichiometry of 1.5 to 3 H+/phosphate transported (2,5,8).…”

“…The observation that Lemna plants, incubated at pH 8, acidify even the bulk of the external solution rather rapidly seems to support this assumption. From the results presented here, it is concluded that, in higher plants, like in bacteria and fungi (2,5,8,18) …”

The mechanism of sodium efflux in yeast

“…Na ÷ enters into the cell through the K ÷ carrier and possibly also through Na*-substrate symporters, as described for phosphate [2]. If Na ÷ can enter into the cell, some mechanisms must exist to exclude the cation and avoid its accumulation.…”

Membrane potential changes during transport of glycine as a neutral amino acid and nitrate in Lemna gibba G 1

“…It seems to operate in the transport of sugars [1][2][3][4][5] and amino acids [8,9] as well as that of anions like phosphate ( [9,10] and C. I. U. E. et al, unpublished results) and nitrate. This assumption would be in agreement with the hypothesis proposed [6] that the proton extrusion pump is the general driving force for active transport in plant cells.…”

“…Not only the uptake of non-electrolytes, but also that of phosphate as an anion was found to be driven by such a mechanism in Lemna (C. I. U. E. et al, unpublished) similar to that in yeast [9,10]. Hence it may be expected that also transport of nitrate is coupled to an ATP-driven H ÷ extrusion pump.…”