Related Experiment Videos
Properties of an abundant RNA-binding protein in yeast mitochondria
P J Dekker1, B Papadopoulou, L A Grivell
1Department of Molecular Cell Biology, University of Amsterdam, The Netherlands.
Abstract:
We have previously identified a protein with Mr approximately 40,000 (p40) that binds with high specificity and affinity to the 5'-untranslated leaders of mitochondrial mRNAs in yeast. Here we show that this protein is abundant, comprising about 0.4% of total mitochondrial protein. p40 is present in a cytoplasmic (rho degree) petite mutant that lacks mitochondrial protein synthesis and is therefore nuclear encoded. p40 can be detected by immunological techniques in cell lysates of several different pet mutants, specifically disturbed in the translation of individual mitochondrial mRNAs. It is thus not one of the translation factors defined by any of these mutations. In the case of a pet111 mutant, which is specifically blocked in the translation of COX2 mRNA, extracts still display COX2 mRNA binding activity, indicating that p40 complex formation in vitro is not dependent on the presence of PET111.
Insights
A nuclear-encoded protein (p40) binds yeast mitochondrial mRNA leaders. This abundant protein is present in mutants lacking mitochondrial protein synthesis, indicating its role in translation regulation.
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Yeast genetics
Background:
- A protein (p40) was previously identified that binds yeast mitochondrial mRNA 5'-untranslated leaders.
- This binding is specific and high-affinity.
Purpose of the Study:
- To characterize the abundance and genetic properties of the p40 protein.
- To investigate the role of p40 in mitochondrial mRNA translation.
Main Methods:
- Quantification of p40 as a percentage of total mitochondrial protein.
- Immunological detection of p40 in various yeast petite mutants (rho degree) affecting mitochondrial translation.
- In vitro mRNA binding assays using cell extracts from specific translation mutants (e.g., pet111).
Main Results:
- p40 is abundant, constituting approximately 0.4% of total mitochondrial protein.
- p40 is nuclear-encoded and present in cytoplasmic petite mutants lacking mitochondrial protein synthesis.
- p40 is detected in mutants specifically defective in the translation of individual mitochondrial mRNAs, suggesting it is not a previously defined translation factor.
- COX2 mRNA binding activity is retained in pet111 mutant extracts, showing p40 complex formation is independent of PET111.
Conclusions:
- p40 is a nuclear-encoded, abundant mitochondrial protein involved in mitochondrial mRNA binding.
- Its presence in translation-defective mutants and independence from specific translation factors like PET111 suggest a regulatory role in mitochondrial translation initiation or efficiency.