Regulation of Mitochondrial Protein Concentration: A Plausible Model Which May Permit Assessing Protein Turnover

Abstract

Publisher Summary This chapter focuses on regulatory controls of mitochondrial protein turnover and measurement of mitochondrial protein degradation. Cell metabolism is mediated by the activity of many enzymes and is controlled by the regulation of key enzyme activities and enzyme levels. Most mitochondrial proteins are coded by nuclear genes and synthesized on cytosolic ribosomes as larger precursors, which then migrate and are imported into mitochondria. The overall protein concentration per cell volume changes very little, although the concentration of individual proteins may do so temporarily. Therefore, protein synthesis and degradation should be closely interrelated. The in vitro protein concentration in mitochondria may be regulated by the entry of mitochondrial protein precursors from the cytosol. Enzymes are flexible molecules whose conformations can be altered upon binding of substrates or other ligands. Mitochondrial proteins are degraded by lysosomes because mitochondria are frequently seen inside autophagic vacuoles. The importance of protein degradation is chiefly as a process to control the concentration of a protein and, thus, cell metabolism. Protein synthesis is usually controlled by regulating the amount of its messenger RNA available for translation.