Oligomycin-sensitivity-conferring protein OSCP

ATP synthase activity can be restored by adding back the F] complex to the depleted membranes. The F[ complexes bind to membrane channels known as the F complex, which are also composed of multiple subunits. The polypeptides of the F0 component are very hydrophobic and form a proton transport channel through the membrane, which links the proton gradient to ATP synthesis. This channel appears to be lined with hydrophilic residues such as seryl, threonyl and carboxyl groups. The stalk that connects the F, to the F complex comprises one copy each of the polypeptide known as the oligomycin-sensitivity-conferring protein (OSCP) and another protein known as F6. 

Mitochondrial ATP synthase of yeast contains at least 13 different kinds of subunits and that of ani-mals 16, twice as many as in E. coli. Subunits a, p, y, a, b, and c of the mitochondrial synthase correspond to those of E. coli. However, the mitochondrial homolog of E. coli 5 is called the oligomycin-sensitivity-conferring protein (OSCP). It makes the ATPase activity sensitive to oligomycin. The mitochondrial 8 subunit corresponds to e of E. coli or of chloroplasts. Mitochondrial e has no coimterpart in bacteria. ... 

In the FoFi-ATPase of mammalian and yeast mitochondria, the oligomy-cin sensitivity conferring protein (OSCP) is one of the subunits of the enzyme complex, and is needed for inhibition of ATP hydrolysis by oligomycin (1). The amino acid sequence of OSCP from beef heart mitochondria is homologous to the amino acid sequence of the S-subunit of the Fi-ATPase from E. coli, 26.4% (2), chloroplasts, 25.3% (3), and Rhodospirill urn rubrum, 28.9% (2). However, only R. rubrum is sensitive to oligomycin (4). It has also been shown that R. rubrum Fj-ATPase, with the B-subunits substituted with B from E. coli, is not oligomycin sensitive when reconstituted to depleted membranes (5). 

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