A yeast mutant temperature-sensitive for mitochondrial assembly is deficient in a mitochondrial protease activity that cleaves imported precursor polypeptides
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Abstract:
We have previously described two yeast mutants which, at elevated temperature, stop growing and accumulate precursors to several imported mitochondrial proteins. We now show that one of these mutants (mas 1) is deficient in a matrix-located protease activity which cleaves the pre-sequences from mitochondrial precursor proteins. Isolated mas 1 mitochondria catalyze oxidative phosphorylation, exhibit respiratory control and import mitochondrial precursor polypeptides, but are defective in removing transient pre-sequences from imported precursors. The phenotype of the mas 1 mutant suggests that the matrix-located processing protease is essential for growth and for mitochondrial assembly.
Insights
A yeast mutant (mas1) lacks a key protease for processing mitochondrial proteins. This defect prevents proper mitochondrial assembly and cell growth, highlighting the protease
Area of Science:
- Mitochondrial biology
- Protein processing
- Yeast genetics
Background:
- Yeast mutants accumulate mitochondrial protein precursors at high temperatures.
- Mitochondrial protein import requires processing of precursor polypeptides.
Purpose of the Study:
- To investigate the molecular basis of the temperature-sensitive growth defect in yeast mutant mas1.
- To identify the function of the protein deficient in mas1 mutants.
Main Methods:
- Characterization of yeast mutant mas1.
- Mitochondrial import assays.
- Protease activity assays on isolated mitochondria.
Main Results:
- The mas1 mutant is deficient in a matrix-located protease activity.
- This protease cleaves pre-sequences from imported mitochondrial precursor proteins.
- mas1 mitochondria import proteins but fail to process them.
Conclusions:
- The matrix-located processing protease is essential for yeast growth.
- This protease plays a critical role in mitochondrial assembly and function.