Coupling between proteolytic processing and translocation of the precursor of the F1-ATPase beta-subunit during its import into mitochondria of intact cells.

The intracellular transport of newly synthesized beta-subunits of the F1-ATPase (beta F1) and of newly synthesized ADP/ATP carrier was followed in isolated rat hepatoma cells. As tested by rapid fractionation of [35S]methionine pulse- and pulse-chase-labeled cells and by sensitivity of labeled polypeptides to externally added protease, the import of beta F1 into mitochondria was strongly inhibited by the additional low concentrations of rhodamine 6G (R6G). In contrast, the import of the ADP/ATP carrier into mitochondria was not affected by the inhibitor. The results imply that the proteolytic processing of the precursor of beta F1 is coupled to its translocation across the mitochondrial membrane.