title: Na+-driven Ca2+ transport in alkalophilic Bacillus.
abstract: Ca2+ transport was studied in membrane vesicles of alkalophilic Bacillus. When Na+-loaded membrane vesicles were suspended in KHCO3/KOH buffer (pH 10) containing Ca2+, rapid uptake of Ca2+ was observed. The apparent Km value for Ca2+ measured at pH 10 was about 7 microM, and the Km value shifted to 24 microM when measured at pH 7.4. The efflux of Ca2+ was studied with Ca2+-loaded vesicles. Ca2+ was released when Ca2+-loaded vesicles were suspended in medium containing 0.4 M Na+. Ca2+ was also transported in membrane vesicles driven by an artificial pH gradient and by a membrane potential generated by K+-valinomycin in the presence of Na+. These results indicate the presence of Ca2+/Na+ and H+/Na+ antiporters in the alkalophilic Bacillus A-007
mesh_terms: D001407:Bacillus / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012964:Sodium / Q000494:pharmacology*
chemical_list: D012964:Sodium; D002118:Calcium