[28] Synthesis and assembly of subunit 6 of the mitochondrial ATPase in yeast

Studies on the assembly of the yeast mitochondrial F0 sector are currently focused on the two polypeptides that are shown to be subunits of the F0 sector. Both are products of the mitochondrial protein synthesis: subunit 6 and subunit 9. This chapter describes the synthesis and assembly of subunit 6. This subunit is a functional component of the mitochondrial H+-adenosine triphosphatase (ATPase). Although it appears that subunit 6 is not required for the formation of the enzyme proton channel, its presence is essential for the coupled ATP synthesis activity of the H+-ATPase. Furthermore, a mutant of yeast with a lesion in the structural gene of subunit 6 has been shown to be defective in oxidative phosphorylation or ATP–Pi exchange activities, although the mutant mitochondria contain an oligomycin-sensitive mitochondrial H+-ATPase, indicating that the F0 and F1 sectors of the enzyme complex are properly assembled. Immunochemical procedures are useful in the study of the assembly of subunit 6.