[Interaction of 3-(3H)-2-n-nonyl-4-hydroxyquinoline-N-oxide with submitochondrial particles of beef heart. III. Correlation between the binding of 3H-NQNO and inhibition of the respiratory activity].

The present work is an extension of our precedent papers (1-3). In the present report the relationship was studied between the inhibition by 3H-NQNO, 3-3H-2-n-nonyl-4-hydroxy-quinoline-N-oxide, of the respiratory activity induced in submitochondrial particles from beef heart by NADH and the binding of 3H-NQNO to the specific binding site. The experiments showed that the concentrations of inhibition sites and of specific binding sites are identical. Titrating the inhibition of NADH-oxidase activity with increasing amounts of 3H-NQNO a close connection was observed between the decrease of the respiratory activity and the increase of the specific binding of 3H-NQNO. When nearly full inhibition (85%) was reached, also the specific binding was saturated. We may conclude that 3H-NQNO behaves like an ideally simple inhibitor: the inhibition of electron transfer by 3H-NQNO is linear with the saturation of the specific binding site.