Characterization of a Membrane-Associated ATPase from Pseudomonas aeruginosa 1

Abstract

Summary

The cell membrane-bound ATP-ase of P. aeruginosa was characterized. It was optimally activated by Mg²⁺ and suboptimally activated by other divalent cations (e.g., Mn²⁺; Ca²⁺, or Zn²⁺) at pH 9. It was not stimulated by Na⁺ or K⁺. Concentrations of divalent cations higher than those required for optimal activation of the ATPase were inhibitory. The ATPase had greatest activity against ATP. Other purine nucleotide triphosphates were hydrolyzed by the ATPase at 30% of the rate of ATP. The ATPase had little or no activity against the pyrimidine nucleoside triphosphates or against ADP. The products of ATP hydrolysis were ADP and inorganic phosphate. No phosphatase or pyrophosphatase activity was detected. The ATPase was not inhibited by ouabain, oligomycin, iodoacetic acid, 2,4-dinitrophenol, Atabrine or KCN. It was strongly inhibited by NaN³, β-chloromercuribenzoic acid (CMB) and ADP and it was weakly inhibited by N-ethylmaleimide (NEM), AMP, and KF. The inhibition by CMB and NEM was reversed by 2-mercaptoethanol. The ATPase appeared to be located on the inner surface of the cell membrane or to have an intramembrane location. The true physiological role for the ATPase was not elucidated by this research.