| Abstract: | 1. Unlike chloroplasts, submitochondrial particles are not uncoupled by nigericin + KCl or NH4Cl. Also the uncoupling effect of lipophilic anions is largely independent of the addition of weak bases. 2. Low concentrations of permeant anions cause a shift of the steady-state energy level rather than a cycle of energy utilization. The degree of inhibition of ATP synthesis by tetraphenylboron is larger than required for the uptake of the anion. 3. Lipophilic anions such as bromthymolblue, bromcresolpurple, and 8-anilino-1-napthalene sulphonate cause a pH-independent, 50% uncoupling in submitochondrial particles at concentrations of 3, 30 and 30 muM, respectively. The passive interaction of bromthymolblue and bromcresolpurple appears as a pH-dependent distribution between two pHases. ATP causes a pH-independent slight shift in the anion distribution, with negligible anion accumulation. 4. Addition of amines to energized submitochondrial particles results in two types of effects; uptake of amines and uncoupling. While in chloroplasts amine uptake and uncoupling are closely associated, this is not the case in submitochondrial particles. The uncoupling effect is observed only with lipophilic and not with hydrophilic amines, and the degree of uncoupling increases with the lipophilicity of the amines. The amine uptake, on the other hand, is accompanied by negligible uncoupling. 5. While the uptake of amines is dependent on the presence of non-permeant anions, such as Cl-, the uncoupling effect is independent of Cl-. Furthermore the amine uncoupling is markedly enhanced by lipophilic anions. 6. The view is discussed that the uncoupling effect of lipophilic anions and lipophilic amines in submitochondrial particles is due to a catalytic energy dissipation rather than to a stoichiometry energy utilization. The molecular mechanism of uncoupling presumably involves a cycling of charges after a perturbation of the membrane structure. |
