JBC, Vol. 251, Issue 4, 962-967, Feb, 1976
Calcium transport driven by a proton gradient and inverted membrane vesicles of Escherichia coli
T. Tsuchiya and B. P. Rosen
Calcium transport into inverted vesicles of Escherichia coli was observed
to occur without an exogenous energy source when an artificial proton
gradient was used. The orientation of the proton gradient was acid inside
and alkaline outside. Either phosphate or oxalate was necessary for
transport, as was found for respiratory-driven or ATP-driven uptake
(Tsuchiya, T., and Rosen, B.P. (1975) J. Biol. Chem. 250, 7687-7692).
Phosphate accumulation was found to occur in conjunction with calcium
accumulation. Calcium transport driven by an artificial proton gradient was
stimulated by dicyclohexylcarbodiimide, an inhibitor of the Mg2+ATPase (EC
3.6.1.3). Valinomycin, which catalyzes electrogenic potassium movement,
stimulated calcium accumulation, while nigericin, which catalyzes
electroneutral exchange of potassium and protons, inhibited both artificial
proton gradient-driven transport and respiratory-driven transport. Other
properties of the proton gradient-driven system and the previously reported
energy-linked calcium transport system are similar, indicating that calcium
is transported by the same carrier whether energy is supplied through an
artificial proton gradient or an energized membrane state. These results
suggest the existence of a calcium/proton antiport.