JBC, Vol. 250, Issue 14, 5370-5374, Jul, 1975
Characteristics of the movement of K+ across the mitochondrial membrane and the inhibitory action of Tl+
H. Barrera and A. Gomez-Puyou
The incubation of mitochondria in mixtures that contain phosphate, NaCl,
oxidizable substrate, and ethylenediaminetetraacetate induces the efflux of
K-+. This process depends on electron transport and on the cyclic movement
of phosphate across the membrane. Sodium ions, Li-+, or Cs-+ to a smaller
extent, are required for maximal release of K-+. Potassium ions do not
induce net efflux of internal K-+, but instead prevent the Na-+-induced
release of K-+. Significant K-+ influx takes place in K-+-depleted
mitochondria through a process with characteristics which are almost
identical with those in which K-+ release takes place. As Na-+ inhibits the
uptake of K-+, it is suggested that the movement of K-+ across the membrane
is controlled by the cationic environment. Thallous ion, at concentrations
that do not affect oxidative phosphorylation, was found to be an effective
inhibitor of the influx and the efflux of K-+. The inhibitory effect of
Tl-+ seems to be specific for K-+ since it does not affect the movement of
Na-+. Mitochondria bind 10 to 15 nmol of 204-Tl-+ per mg of protein through
an energy-independent process.
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