A Ca 2+ indicator arsenazo III was used to demonstrate calcium uptake activity of symbiosomes and the peribacteroid membrane (PBM) vesicles isolated from broad bean root nodules and placed in the medium containing ATP and Mg 2+ ions. This process was shown to be rapidly stopped by vanadate, completely reversed in the presence of the calcium ionophore A23187 but insensitive to agents abolishing electrical potential or pH difference across the PBM. The presence of an endogenous calcium pool within isolated symbiosomes and bacteroids was detected using a Ca 2+ indicator chlortetracycline. These results prove a primary active transport of Ca 2+ through the PBM of legume root nodules and provide the first functional identification of an ATP-driven Ca 2+ -pump, most likely Mg 2+ -dependent Ca 2+ -translocating ATPase, in this membrane. z 1999 Federation of European Biochemical Societies.

No abstract

No abstract

No abstract

No abstract