Inhibition of membrane-bound wild type and mutant ATP synthase by
NBD-Cl. The membranes were preincubated for 60 min at room temperature
with varied concentration of NBD-Cl, and then aliquots added to 1 ml of assay
buffer and ATPase activity were determined. The details are given under
“Materials and Methods.” •, wild type; ○, αS347A;
□, αS347Q; ▵, αG351Q. Each data point represents an
average of at least four experiments, using two independent membrane
preparations of each mutant. The results agreed within ±10%.