The Metabolism of Mitochondrial Proteins

Abstract

The turnover rates of six protein fractions of rat liver mitochondria were estimated from the incorporation of 14C-carbonate given continuously. The rates were similar and little heterogeneity was evident. When expressed as half-lives, the values ranged from 4 to 6 days. However, the turnover rates of two inducible mitochondrial enzymes, alanine and ornithine aminotransferase, were much faster. The half-lives ranged from 0.73 to 1.03 days. Zonal gradient centrifugation of mitochondria from treated animals indicated that the changes in enzyme activity were occurring in all of the mitochondria at the same rapid rate. The evidence from these experiments suggests that all mitochondria are in a dynamic state and that alteration of the enzyme complement is independent of mitochondrial genesis.