Valinomycin-Induced Uptake of Potassium in Membrane Vesicles from Escherichia coli

Osmotically shocked Escherichia coli and membrane vesicle ghosts from E. coli cells have lost the ability to accumulate potassium by active transport. The addition of valinomycin to the membrane ghosts restores the capacity to accumulate radioactive (42)K and (86)Rb by a temperature- and energy-dependent process. Membrane vesicles prepared from mutants of E. coli altered in potassium transport show defects in the valinomycin-stimulated accumulation of (42)K that are related to the defects in the intact cells.