Transport of prepro-albumin into inverted vesicles prepared from the inner membrane of rat liver mitochondria

When inverted vesicles prepared from the inner membrane of rat liver mitochondria were incubated with prepro-rat serum albumin, considerable amounts of prepro-albumin and pro-albumin were recovered with the inverted vesicles re-isolated by centrifugation. Pro-albumin was resistant to trypsin, but prepro-albumin was completely digested by trypsin, indicating that prepro-albumin was transported into the vesicles and concomitantly converted to pro-albumin. This transport process required ATP, but not a membrane potential. These results suggest that some export machinery for a protein having an amino acid sequence in its N-terminal portion similar to the signal sequence of secretory protein exists in the inner mitochondrial membrane.