Figure 5
Protection of ATPase from DCCD inhibition by Na+at pH 7.6 and pH 9.0. The purified ATPase was incubated with 200 μM DCCD in either 20 mM Tris-HCl, pH 7.6 (A) or 20 mM Tricine-KOH, pH 9.0 (B). The individual mixtures contained the following additions of NaCl: no NaCl added (open circle), 1 mM NaCl (closed triangle), 10 mM NaCl (open triangle) and 50 mM NaCl (closed square). The residual ATPase activity of samples (30 ug protein) taken at the indicated times was determined in the reaction mixture containing 20 mM Tris-HCl pH 7.6, 5 mM MgCl2. The reaction was started by the addition of 4 mM ATP (Tris salt). One hundred percent activity corresponded to 437 nmol min-1 (mg protein)-1. Control without DCCD (closed circle). All data are the average of three independent experiments with vertical bars representing standard errors.