期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：6
页码：1869-1873
DOI：10.1073/pnas.79.6.1869
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A large fraction (30-50%) of the various proteins synthesized within isolated rat liver mitochondria were degraded to amino acids within 60 min after synthesis. Incomplete mitochondrial polypeptides resulting from the incorporation of puromycin were degraded even more extensively (80% per hr). Protein breakdown was measured by the appearance of acid-soluble radioactivity and by the disappearance of labeled polypeptides detected on NaDodSO4/polyacrylamide gel electrophoresis. The amino acids generated by proteolysis were transported rapidly out of the mitochondria and no peptide intermediates accumulated in the organelle. This degradative process did not involve lysosomes or lysosomal enzymes and was markedly stimulated by ATP either generated within the mitochondria or supplied exogenously. An inhibitor of respiration (cyanide) or uncouplers of oxidative phosphorylation (oligomycin, dinitrophenol) reduced proteolysis when mitochondria were provided substrates for ATP generation. When exogenous ATP was provided, these agents did not affect proteolysis, but degradation was then sensitive to atractyloside, an inhibitor of adenine nucleotide transport. Vanadate, an inhibitor of various ATPases, blocked proteolysis even in the presence of ATP and caused a marked stabilization of nearly all polypeptide bands. Thus, mitochondria--like bacteria or the cytosol of animal cells--contain a pathway for complete degradation of proteins which seems to selectively remove polypeptides with abnormal structures. Within this organelle, ATP hydrolysis appears necessary for an initial step in this degradative process.
