Antibiotic inhibitors of mitochondrial ATP synthesis.

Fourteen antibiotics have been found to inhibit oxidative phosphorylation and uncoupler-stimulated adenosinetriphosphatase in mitochondria. Four different types of binding sites for these inhibitors have been found. The first (1) binds aurovertin to purified MF1 ATPase in the stoichiometric ratio of two aurovertin molecules per molecule of ATPase. Site II is the locus for efrapeptin (A23871) and may be a catalytic site on purified ATPase. The remaining two sites have been demonstrated only in mitochondria or submitochondrial particles when the APTase is bound to other membrane components. Oligomycin, venturiciden, venturicidin X and ossamycin probably all bind at site III. Leucinostatin (A20668) binds at site IV. At low concentrations, this antibiotic acts like oligomycin; at higher concentrations it uncouples oxidative phosphorylation. Venturicidin appears to prevent leucinostation from binding at site IV for it allows uncoupling to occur at very low concentrations of the latter antibiotic. Venturicidin aglycone, which is a more effective inhibitor than its parent compound, does not exert this effect. It is concluded that sites III and IV are in juxtaposition and that when venturicidin binds at site III its sugar moiety projects into the area of site IV to prevent leucinostation from binding at its inhibitory site.