Table 3.

Influence of membrane potential and pH gradient on the activity of reconstituted AtUCP1 and AtUCP2

The exchanges were started by adding 0.8 mm [¹⁴C]aspartate or 0.8 mm [¹⁴C]malate to AtUCP1- and AtUCP2-reconstituted proteoliposomes. For the measurements of the aspartate/glutamate carrier activity, 50 μm [¹⁴C]aspartate was added to proteoliposomes reconstituted with AGC2-CTD. K_in⁺ was in included as KCl in the reconstitution mixture, whereas K_out⁺ was added as KCl together with the labeled substrate. Valinomycin or nigericin was added in 10 μl ethanol/ml of proteoliposomes, whereas the control samples contained the solvent alone. 20 mm or 2 mm PIPES (pH 7.0) was present inside and outside the proteoliposomes in the experiments with valinomycin or nigericin, respectively. The exchange reactions were stopped after 7, 20, and 30 s for AtUCP1, AtUCP2, and AGC2-CTD, respectively. The values are means ± S.E. of four independent experiments carried out in duplicate.