Affinity labeling of yeast mitochondrial adenosine triphosphatase by reduction with [3H]borohydride.

Oligomycin-sensitive adenosine triphosphatase (ATPase) has been purified in large yields from yeast mitochondria by a procedure employing Sepharose 6B chromatography. The nature of the oligomycin binding site in this purified preparation has been studied by an affinity labeling technique in which oligomycin binding to the ATPase complex was followed by reduction of the complex with sodium [³H]borohydride. A major incorporation of label into protein with a molecular weight near 8000 was noted. This incorporation is dependent on the presence of oligomycin, is blocked by dicyclohexylcar-bodiimide, and is altered by mutations conferring oligomycin resistance to the ATPase. The evidence suggests that the low molecular weight proteolipid component of the ATPase complex is the site of oligomycin binding.