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Can foreign proteins imported into yeast mitochondria interfere with PIM1p protease and/or chaperone function?
A S Saveliev1, I E Kovaleva, L A Novikova
1Belozersky Institute of Physico-Chemical Biology, Lomonosov State University, Moscow, 119899, Russia.
Abstract:
When studying the fate of mammalian apocytochrome P450scc (apo-P450scc) imported in small amounts into isolated yeast mitochondria, we found that it undergoes degradation, this process being retarded if recipient mitochondria are preloaded in vivo (to about 0.2% of total organelle protein) with a fusion protein composed of mammalian adrenodoxin reductase and adrenodoxin (AdR-Ad); in parallel we observed aggregation of apo-P450scc. These effects suggest some overload of Pim1p protease and/or mtHsp70 system by AdR-Ad, as both of them are involved in the degradation of apo-P450scc (see Savel'ev et al. J. Biol. Chem. 273, 20596-20602, 1998). However, under the same conditions AdR-Ad was not able to impede the import of proteins into mitochondria and the development of the mitochondrial respiratory machinery in yeast, the processes requiring the mtHsp70 system and Pim1p, respectively. These data imply that chaperones and Pim1p protease prefer their natural targets in mitochondria to imported foreign proteins.
Insights
Mammalian apocytochrome P450scc (apo-P450scc) degradation in yeast mitochondria is slowed by a fusion protein (AdR-Ad). However, this protein does not hinder essential mitochondrial functions, suggesting chaperones and proteases prioritize native substrates.
Area of Science:
- Mitochondrial Biology
- Protein Degradation
- Molecular Chaperones
Background:
- Mitochondrial protein import and degradation are crucial for cellular homeostasis.
- The Pim1p protease and mtHsp70 system are key players in mitochondrial protein quality control.
- Understanding substrate specificity of these systems is vital for comprehending mitochondrial function.
Purpose of the Study:
- To investigate the effect of a preloaded fusion protein (AdR-Ad) on the degradation of imported mammalian apocytochrome P450scc (apo-P450scc) in yeast mitochondria.
- To determine if AdR-Ad interferes with essential mitochondrial processes dependent on Pim1p and mtHsp70.
- To explore the substrate preference of mitochondrial chaperones and proteases.
Main Methods:
- Import of mammalian apo-P450scc into isolated yeast mitochondria.
- Preloading mitochondria with a fusion protein of mammalian adrenodoxin reductase and adrenodoxin (AdR-Ad).
- Assessing apo-P450scc degradation and aggregation.
- Evaluating the impact of AdR-Ad on mitochondrial protein import and respiratory machinery development.
Main Results:
- Preloading yeast mitochondria with AdR-Ad retarded the degradation of imported apo-P450scc and induced its aggregation.
- These effects suggest a potential overload of the Pim1p protease and/or mtHsp70 system by AdR-Ad.
- AdR-Ad did not impede protein import into mitochondria or the development of the mitochondrial respiratory machinery.
- Mitochondrial chaperones and Pim1p protease showed preference for native substrates over imported foreign proteins.
Conclusions:
- Mitochondrial chaperones and proteases exhibit substrate specificity, prioritizing endogenous targets.
- Overloading these systems with foreign proteins can affect the degradation of other imported proteins.
- The study provides insights into the selectivity of mitochondrial protein quality control mechanisms.