Uni-site catalysis by Escherichia coli F1-ATPase with different numbers of bound nucleotides.

We prepared two types of E. coli F1 by slightly different gel filtration procedures of the purified F1: F1(II) contained about 2 mol, and F1(V) about 5 mol of bound adenine nucleotides per mol of the enzyme. Thus F1(II) had more than 2, possibly 3, vacant catalytic sites, while F1(V) had less than one vacant catalytic site. The rate of ATP hydrolysis in uni-site catalysis (in the presence of inorganic phosphate) was about 3-fold higher with F1(II) than with F1(V), suggesting that ADP and inorganic phosphate bound at the catalytic sites of F1(V) changed the kinetics of uni-site catalysis significantly.