The inhibition of beef heart mitochondrial F1 by exchange-inert metal-nucleotide complexes was examined. Mono- and bidentate Cr(NH3)4ATP were found to be mixed noncompetitive inhibitors of F1-catalyzed ATP hydrolysis (values of Ki = 0.5 and 0.1 mM; values of α = 0.2 and 24, respectively). Rh(H2O)nATP was also found to be a mixed noncompetitive inhibitor of F1-catalyzed ATP hydrolysis (Ki = 0.3 mM, α = 0.7). These compounds were used in a series of dual inhibition experiments, along with mono- and bidentate CrATP and Co(NH3)4ATP. All the exchange-inert metal-nucleotides examined were found to be mutually exclusive inhibitors of F1, indicating that they all bind to the same site(s). It is postulated that the pKa of the metal-coordinated ligands is related to the potency of inhibition by these compounds. It appears probable that the exchangeinert nucleotide complexes are binding to site(s) in addition to the catalytic site(s) of F1.
ASJC Scopus subject areas
- Molecular Biology