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Gene MRP-L4, encoding mitochondrial ribosomal protein YmL4, is indispensable for proper non-respiratory cell
H R Graack1, L Grohmann, M Kitakawa
1Institut für Genetik, Freie Universität Berlin, Germany.
Abstract:
In order to characterize individual protein components of the mitochondrial (mt) ribosome for regulatory, functional and evolutionary studies, the yeast nuclear gene MRP-L4 (accession No. Z30582), coding for the mt ribosomal protein (MRP) YmL4, has been cloned using oligodeoxyribonucleotides (oligos) deduced from a partial amino acid (aa) sequence [Graack et al., FEBS Lett. 242 (1988) 4-8] as screening probes. MRP-L4 is located on chromosome XII and codes for a slightly basic protein of 319 aa. The first 14 aa have not been found in the mature protein, and putatively form a signal peptide that is cleaved off during or after mt import. YmL4 has an N terminus very rich in Pro residues, and at its C terminus contains four hydrophobic domains. YmL4 shows no significant sequence similarity to any other sequence from the databases. Gene disruption shows the MRP-L4 product to be indispensable for mt function in cells growing on non-fermentable carbon sources. In contrast to nearly all other MRPs investigated so far, gene disruption of MRP-L4 also affects growth of yeast cells on fermentable carbon sources, suggesting additional cytosolic and/or mt functions of YmL4 besides its involvement in mt protein biosynthesis.
Insights
The mitochondrial ribosomal protein YmL4 is essential for yeast cell growth. Gene disruption reveals YmL4 has roles beyond mitochondrial protein synthesis, impacting both mitochondrial and cytosolic functions.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Mitochondrial ribosomes (mitoribosomes) are crucial for cellular energy production.
- Characterizing individual mitoribosome proteins aids in understanding regulation, function, and evolution.
- The yeast nuclear gene MRP-L4 encodes the mitoribosomal protein YmL4.
Purpose of the Study:
- To clone and characterize the yeast nuclear gene MRP-L4.
- To investigate the function of the mitoribosomal protein YmL4 in yeast cells.
- To explore potential roles of YmL4 beyond mitochondrial protein biosynthesis.
Main Methods:
- Oligodeoxynucleotide screening to clone the MRP-L4 gene.
- Gene sequencing to determine the protein structure (319 amino acids).
- Gene disruption experiments to assess the impact on cell growth and mitochondrial function.
Main Results:
- The MRP-L4 gene was cloned and found to encode YmL4, a protein with a putative signal peptide and unique structural features.
- YmL4 exhibits no significant sequence similarity to other known proteins.
- Disruption of MRP-L4 renders cells unable to grow on non-fermentable carbon sources, indicating essentiality for mitochondrial function.
- MRP-L4 gene disruption also impairs growth on fermentable carbon sources, suggesting additional cellular roles.
Conclusions:
- The mitochondrial ribosomal protein YmL4 is indispensable for yeast mitochondrial function.
- YmL4 possesses functions beyond its role in mitochondrial protein biosynthesis, affecting both mitochondrial and potentially cytosolic processes.
- Further research is warranted to elucidate the multifaceted roles of YmL4 in cellular physiology.