Mechanism of inhibition of mitochondrial adenosine triphosphatase by dicyclohexylcarbodiimide and oligomycin: relationship to ATP synthesis.

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Measurement of the rate of [gamma-32P]ATP binding (k1) and release (k-1) from catalytic sites on submitochondrial particles permitted calculation of the affinity constant in catalytic sites (k1 = K1/k1-1) of 10(12) M-1. This value is the same as that determined previously for the solubilized ATPase (F1) from beef heart mitochondria. Treatment of submitochondrial particles with dicyclohexylcarbodiimide or oligomycin so as to cause about 90% inhibition of ATPase activity was accompanied by a decrease in the binding of [gamma-32P]ATP in high-affinity catalytic sites. Under the conditions of the experiment, it is expected that the inhibitors reacted not with the ATPase itself but with other proteins in the oligomycin-sensitive ATPase complex (F0-F1). It is proposed that dicyclohexylcarbodiimide and oligomycin inhibit ATPase activity by causing a conformational change in the F0 portion of the complex that is transmitted to F1, resulting in an impaired binding of substrate in catalytic sites. These observations of apparent conformational interactions between F0 and F1 on the mitochondrial membrane are relevant to the mechanism of the coupling device that links the energy store to ATP formation in oxidative phosphorylation. It is proposed that a change in the state of ionization of one or more charged amino acid residues in F0 results in a conformational change in F0 which, transmitted to F1, reversibly alters the catalytic sites and facilitates the release of product ATP.

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