Proton-coupled calcium transport by intact cells of Azotobacter vinelandii.
Addition of ionophores to resting aerobic cultures of Azotobacter vinelandii OP resulted in 45Ca2+ uptake (Km = 60 microM Ca2+; Vmax 1.1 nmol/min per mg of cell protein) which was inhibited by cations (La3+ greater than Mn2+ greater than Sr2+ greater Ba2+). The rate of Ca2+ entry correlated with the magnitude of a transmembrane proton gradient (inside acid) which developed in the respective order: valinomycin less than tetrachlorosalicylanilide less than nigericin less than gramicidin D less than tetrachlorosalicylanilide plus valinomycin. A process of calcium-proton exchange (antiport) is responsible for calcium accumulation under these conditions.
D000693:Anaerobiosis; D017920:Antiporters; D001395:Azotobacter / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D027682:Cation Transport Proteins; D002412:Cations / Q000494:pharmacology; D003593:Cytoplasm / Q000502:physiology; D006096:Gramicidin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D008744:Methylamines / Q000378:metabolism; D009550:Nigericin / Q000494:pharmacology
D017920:Antiporters; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D002412:Cations; D007476:Ionophores; D008744:Methylamines; C027614:calcium-hydrogen antiporters; D006096:Gramicidin; D009550:Nigericin; D002118:Calcium