INVITRO DEGRADATION OF MITOCHONDRIAL PROTEINS BY ATP-DEPENDENT PROTEASE IN BOVINE ADRENAL-CORTEX

We have examined in vitro degradation of mitochondrial proteins by ATP -dependent protease in bovine adrenal cortex. Purified ATP-dependent p rotease degraded at least five proteins in vitro in the presence of AT P and Triton X-100 using mitochondrial fraction as a substrate. Two of the degraded proteins were identified as P-450SCC and adrenodoxin red uctase by immunoblotting. No degradation of P-45011beta or adrenodoxin was detected. Purified P-450SCC and adrenodoxin reductase were also d egraded. By analyzing degradation products of P-450SCC we identified 4 9 peptides and 59 cleavage sites. The size of the products was between 3 and 18 amino acid residues. The protease preferentially cleaved the carboxy-side of Leu, Phe, Ala, Val, Met, and some other amino acids. Since the protease (a matrix enzyme) is accessible to P-450SCC and adr enodoxin reductase localized on the matrix side of inner membrane, the present results suggest that the protease might participate in the tu rnover of these two proteins and some other mitochondrial proteins.