Turnover of mitochondrial inner membrane proteins in hepatoma monolayer cultures.
The degradation rates of inner mitochondrial membrane proteins were examined in serum-deprived hepatoma cultures. In those nonproliferating cells, the degradation of composite mitochondrial proteins was a first order process with a half-life of 34 h. The half-lives of specific inner mitochondrial membrane polypeptides were determined by examining the 3H/35S of isolated polypeptides from cells given [3H]methionine and [35S]methionine pulses, respectively, before and after a 2-day chase period. The 33 most abundant polypeptides resolved on a bidirectional polyacrylamide gel system showed half-lives ranging from 20 to 100+ h. The 15 polypeptides translated on mitochondrial ribosomes in the presence of inhibitory concentrations of cycloheximide also displayed heterogeneous rates of degradation (t1/2 = 35-100+ h). None of the isolated adenosine triphosphatase (coupling factor F1) or immunoprecipitated cytochrome c oxidase subunits were significantly turned over during the case period. Five of eight cytochrome b-c1 complex subunits, however, were turned over significantly more rapidly (t1/2 = 39-42 h) than the other three (t1/2 = 94+ h). The results demonstrate heterogeneous degradation rates for inner membrane polypeptides, extending in some cases to those within the same respiratory complex.
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D003580:Cytochromes / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D010086:Oxidative Phosphorylation Coupling Factors / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D014176:Protein Biosynthesis; D006180:Proton-Translocating ATPases; D051381:Rats
D003580:Cytochromes; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D010086:Oxidative Phosphorylation Coupling Factors; D010455:Peptides; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases