Uncoupler-reversible inhibition of mitochondrial ATPase by metal chelates of bathophenanthroline. II. comparison with other inhibitors

(1) Trisbathophenanthroline-Fe²⁺(BPh₃Fe²⁺) alters the hyperbolic relationship between concentration of ATP and reaction velocity of F₁-ATPase to sigmoidal, with a simultaneous decrease in maximal velocity. (2) BPh₃Fe²⁺ binds to the β-subunit of F₁ and competes with the binding of aurovertin. The reversal of this effect by uncouplers in enhanced by ADP and diminished by ATP. BPh₃Fe²⁺ also changes the hyperbolic concentration dependence of aurovertin binding to sigmoidal. (3) BPh₃Fe²⁺ stabilizes F₁ against cold inactivation and cold dissociation in an uncoupler-reversible manner. (4) BPh₃Fe²⁺ efficiently protects F₁ against the light-induced inactivation occurring in the presence of Rose Bengal, and the effect is reversed by uncouplers. (5) The results are discussed in relation to the reaction mechanism of F₁-ATPase and other enzymes catalyzing the reversible hydrolysis of pyrophosphate bonds.