INHIBITORY EFFECT OF NAN3 ON THE F0F1 ATPASE OF SUBMITOCHONDRIAL PARTICLES AS RELATED TO NUCLEOTIDE-BINDING

The inhibitory effects of NaN3 on the F0F1 ATPase of beef heart submit ochondrial particles were investigated. It was shown that NaN3 inhibit ed the ATPase activity only in the presence of ATP or ADP and the inhi bition proceeded slowly. Analysis of the time-course of the inhibition process lead to a conclusion that an ATP binding site which has an ap parent K(d) of 14.0 +/- 8.7 muM is responsible for the increase of NaN 3 sensitivity. This value agreed well with the low K(m) of ATP hydroly sis characterized before (Muneyuki, E., and Hirata, H. (1988) FEBS Let t. 234, 455-458) and in the range of so-called bi-site catalysis. The same conclusion was derived as for isolated F1 ATPase. From similar an alysis, the K(d) of this site for ADP was deduced to be 1.34 +/- 0.45 muM, which also agreed with that reported by Pedersen (Pedersen, P.L. (1975) Biochem. Biophys. Res. Commun. 64, 610-616) and also in the sam e range as reported for the low K(m) of ATP synthesis by activated sub mitochondrial particles. These results suggest that hydrolysis through the low K(m) mode of ATPase reaction leads the enzyme NaN3 sensitive form and this reaction cycle corresponds to the low K(m) mode of ATP s ynthesis.