Anion regulation of the mitochondrial F1FoATP-synthase

ANABELLA F. LODEYRO; OSCAR A. ROVERI

Buenos Aires, ARGENTINA

Congreso; XIV Congreso Internacional de Biofísica; 2002

International Union for Pure and Applied Biophysics, Sociedad Argentina de Biofísica

ANION REGULATION OF THE MITOCHONDRIAL F1FoATP-SYNTHASE The mitochondrial F1FoATP-synthase catalyses DmH+-driven ATP synthesis and DmH+-generating ATP hydrolysis. The isolated F1 retains only the ability of hydrolyzing ATP, activity that is affected by bicarbonate and sulfate among other anions. Bicarbonate is an activating anion of ATP hydrolysis that inhibits ATP synthesis in beef-heart submitochondrial particles (SMP). The inhibition is competitive with respect to ADP and non-competitive towards Pi. (Lodeyro et al. (2001) Biochim. Biophys. Acta 1506, 236–243). It has been reported that sulfate inhibits ATP hydrolysis in yeast F1 (Recktenwald and Hess 1977 FEBS Lett 76, 25–28). We report here a detailed kinetic study of its effect on the ATPase activity of beef-heart mitochondrial F1 and on ATP synthesis in SMP. At [ATP] < 2 mM sulfate was a partial inhibitor of ATP hydrolysis, whereas it behaved as a non essential activator at higher [ATP]. ATP synthesis was strongly inhibited by sulfate. The inhibition was linear competitive with respect to Pi and mixed towards ADP. Non parallel 1/v vs [SO42-] plots were obtained at different fixed [HCO3-]. In summary: i) sulfate does not bind to a catalytic site; ii) the complex kinetic behavior observed strongly suggests that the anion binds to more than one site in F1; iii) bicarbonate and sulfate can bind simultaneously to F1.