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A model is presented for the energy linked accumulation of cations. It is assumed that the H+ carrier is energized at the inner surface and acquires an increased nucleophilicity. The translocation of the protonated carrier to the outer surface involves a de-energization. Kinetic equations have been developed and have been tested in respect to several parameters of the process of active transport. The effects of the internal and external K+ and H+ concentrations and of valinomycin are in agreement with the predictions of the equations. Also, in agreement with the model, there is competition of divalent cations with the K+ uptake. The steady state respiration of valinomycin treated mitochondria is shown to be very low although there is a large K+ concentration gradient. Swelling of mitochondria causes a considerable increase in the steady state respiration. There is a parallel lowering of the K+ concentration gradient. By measuring the P/O ratio in valinomycin treated mitochondria it is found that phosphorylation is abolished only when the proton motive force, calculated according to Mitchell, becomes lower than 122 mV. The low rate of state 4 respiration is assumed in the present model, where the thermodynamic potential of the internal cations is higher than that of the external ones, to be a function of the amount of carrier in the energized and ground states. The steps involved in the transmembrane K+ translocation are also analyzed by using inhibitors of the surface binding, such as Li+, and of the translocation of cations in the hydrophobic phase, such as local anesthetics. It is concluded that three steps in series are involved for the cation translocation. These occur at the surface of the mitochondria, in the hydrophobic phase and at the carrier level.
Massari et al. (Sun,) studied this question.