Abstract
Intact cells of a H+-translocating ATPase-deficient strain of Escherichia coli were starved of endogenous energy reserves and passively loaded with 45CaCl2. Energy-dependent efflux of calcium was observed upon addition of glucose or respiratory substrates. Addition of cyanide or uncouplers prevented efflux. It is concluded that calcium efflux in intact cells is coupled to the proton motive force via secondary calcium-proton exchange.