The characterization of mitochondrial translation products in rat liver and rat hepatoma cells

Kolarov, Jordan; Kuźela, S; Wielburski, Antek; Nelson, Bruce R.

doi:10.1016/0014-5793(81)81033-2

Cited by 17 publications

(4 citation statements)

References 23 publications

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“…Their Mr were 10,000-20,000, 20,000, 25,000, 32,000, and 38,000-40,000 ( Fig. 2A) in accord with published data for proteins synthesized in mammalian mitochondria (43)(44)(45)(46)(47). No single polypeptide was specifically degraded; instead, all five radioactive bands disappeared to a similar extent when the labeled mitochondria were incubated in the presence ofATP ( Fig.…”

Section: Resultssupporting

confidence: 79%

Liver mitochondria contain an ATP-dependent, vanadate-sensitive pathway for the degradation of proteins.

Desautels¹,

Goldberg²

1982

Proc. Natl. Acad. Sci. U.S.A.

114

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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.The proteins comprising the mitochondria, like other proteins in mammalian cells, are subject to continual turnover (1). It has generally been assumed that mitochondria are degraded within the lysosome (2-5), and under certain conditions whole mitochondria or mitochondrial enzymes have been demonstrated within autophagic vacuoles (2-4). However, different mitochondrial proteins turn over at distinct rates. Outer membrane proteins tend to be degraded at a faster rate than those of the inner membrane (6). Furthermore, individual proteins within the same mitochondrial compartment can also have different turnover rates. In the matrix, several enzymes have tl/2 ranging from 70 min to 1-2 days, whereas the bulk of mitochondrial proteins turn over with a tl/2 of 3-5 days (6-8). Such observations cannot be explained by indiscriminate degradation of this organelle within the lysosome.One possible explanation for this heterogeneity in degradative rates is that proteins may be excreted by the mitochondria for degradation in the cytoplasm or lysosome. Another possibility is that there exists within mitochondria a proteolytic system that selectively hydrolyzes the short-lived enzymes. Several groups have reported proteases associated with the mitochondrial fraction of mammalian cells (9-14). However, an intramitochondrial localization has not been demonstrated definitively for any of these enzymes. The presence in the mitochon...

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Section: Resultssupporting

confidence: 79%

Liver mitochondria contain an ATP-dependent, vanadate-sensitive pathway for the degradation of proteins.

Desautels¹,

Goldberg²

1982

Proc. Natl. Acad. Sci. U.S.A.

114

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“…1). This molecular weight pattern agrees approximately with that observed for rat hepatoma mitochondria) translation products by Kolarov et al (9). These workers obtained five prominent bands on one-dimensional SDS electrophoretic gels: a diffuse band at 39,000 mol wt and bands at 23,000 and 21,000 mol wt corresponding to the three subunits of cytochrome oxidase ; a band at 21,000 mol wt corresponding to a subunit of the ATPase; a band at 32,000 mol wt corresponding to a subunit of the cytochrome b-cl complex, and an unassigned band of relatively high molecular weight.…”

Section: Resultssupporting

confidence: 92%

Selective synthesis of mitochondrial proteins by Chinese hamster ovary cells severely starved for various amino acids.

Chamberlain¹,

Pollard²,

Stanners³

1984

The Journal of Cell Biology

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“…Mammalian cytochrome oxidase has, however, a total of 13 nonidentical subunits (Kadenbach et al, 1983). In eukaryotes, the three largest are encoded by the mitochondrial DNA, and the remaining are nuclear-encoded (Sebald et al, 1972;Mason & Schatz, 1973;Kolarov et al, 1981). Oxidases such as those from yeast (Power et al, 1984) and plants (Matsuoka et al, 1981;Nakagawa et al, 1987) share similar mitochondrial subunits to the beef heart, but contain dissimilar nuclear subunits.…”

mentioning

confidence: 99%

Structurally unique plant cytochrome c oxidase isolated from wheat germ, a rich source of plant mitochondrial enzymes

Peiffer¹,

Ingle²,

Ferguson‐Miller³

1990

Biochemistry

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Purification and characterization of plant cytochrome c oxidases have been impeded by the difficulty of obtaining enough plant mitochondria. We have found commercial wheat germ to be a rich and convenient source of mitochondrial membranes containing respiratory chain complexes in ratios and amounts similar to mitochondria prepared from etiolated seedlings. Cytochrome c oxidase was purified from these membranes by anion-exchange (MonoQ) fast protein liquid chromatography. The enzyme is highly active (turnover number up to 1000 s-1) and exhibits biphasic cytochrome c reaction kinetics similar to those of beef heart oxidase. As with other plant oxidases, the visible spectrum of wheat germ oxidase in the reduced form is blue-shifted compared to other eukaryotic cytochrome oxidases, with peaks at 441 and 602 nm. The electron paramagnetic resonance spectrum of CuA of the wheat germ enzyme is very similar to that of the maize and beef heart enzymes, suggesting that the copper environment is not altered. Sodium dodecyl sulfate-polyacrylamide gels show a subunit composition in which subunits I-IV resemble those of the yeast enzyme in size and antigenicity, while three to four smaller peptides are dissimilar to yeast and other eukaryotic oxidases. A difference between the subunit composition of the wheat germ and wheat seedling enzymes suggests the existence of a developmental or tissue-specific form of cytochrome oxidase in plants.

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The characterization of mitochondrial translation products in rat liver and rat hepatoma cells

Cited by 17 publications

References 23 publications

Liver mitochondria contain an ATP-dependent, vanadate-sensitive pathway for the degradation of proteins.

Liver mitochondria contain an ATP-dependent, vanadate-sensitive pathway for the degradation of proteins.

Selective synthesis of mitochondrial proteins by Chinese hamster ovary cells severely starved for various amino acids.

Structurally unique plant cytochrome c oxidase isolated from wheat germ, a rich source of plant mitochondrial enzymes

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