Sep 21, 1976

Molecular polymorphism and mechanisms of activation and deactivation of the hydrolytic function of the coupling factor of oxidative phosphorylation

R Adolfsen, E N Moudrianakis


The 13S coupling factor of oxidative phosphorylation from Alcaligenes faecalis has a latent adenosine triphosphatase (ATPase) function that can be activated by heating at 55 degrees C for 10 min at pH 8.5 in 50% glycerol. The specific activity increases from 0.1 to 20--30 mumol min-1 mg-1. Adenosine 5'-triphosphate (ATP) is not required for stabilization at 55 degreesC when glycerol is present. Activation involves displacement of the endogenous ATPase inhibitor subunit (epsilon subunit), and readdition of this subunit results in deactivation. In the deactivation process the ATPase inhibitor subunit can be replaced by other cationic proteins such as protamine, histones, or poly(lysine). Mg2+ and H+ also are effective deactivators. The fact that every positively charged substance tested deactivated the enzyme suggests that the inhibitor subunit is complexed with the enzyme at a site containing a surplus of negative charges. The activated enzyme is not labile, but it is salt labile, having a half-life of 2-3 min in 0.1 M KI at either 25 or 0 degrees C. The activated ATPase is also inhibited by aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD), and by the cross-linking agent dimethyl suberimidate. Evidence for polymorphism ...Continue Reading

Mentioned in this Paper

Adenosine Triphosphatases
Alcaligenes faecalis
MUC7 gene
Dimethyl Suberimidate
Oxidative Phosphorylation

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