Mmf1p, a novel yeast mitochondrial protein conserved throughout evolution and involved in maintenance of the mitochondrial genome
| Autor: | Ilaria Malanchi, K. J. Blight, Antonio Marchini, L. Jaquet, J. C. Jauniaux, M. A. N. Hajibagheri, Massimo Tommasino, Francesca Magherini, Ellinor Oxelmark |
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| Jazyk: | angličtina |
| Rok vydání: | 2000 |
| Předmět: |
DNA Replication
Signal peptide Saccharomyces cerevisiae Proteins Protein family Molecular Sequence Data Saccharomyces cerevisiae Biology Cell Biology Genetics Molecular Biology DNA Mitochondrial Antibodies Conserved sequence Evolution Molecular Fungal Proteins Mitochondrial Proteins Bacterial Proteins Heat shock protein Cell and Organelle Structure and Assembly Protein biosynthesis Animals Humans Amino Acid Sequence Cloning Molecular Peptide sequence Conserved Sequence Genome Proteins Intracellular Membranes Hmg protein Mitochondria Rats Transport protein Cell biology Microscopy Electron Protein Transport Phenotype Solubility Sequence Alignment Gene Deletion |
| Popis: | Proteins with a key role in central cellular pathways are highly conserved throughout evolution. Recently, a novel family of small proteins (p14.5, or YERO57c/YJGFc) has been identified in bacteria and in lower and higher eukaryotes (14, 19, 23, 25). They have similar primary structures and molecular masses of approximately 15 kDa. Several independent studies have provided conflicting evidence concerning the hypothetical biological function(s) of these proteins. Initial studies suggest that the rat member of this family, rp14.5, may belong to the high-mobility group (HMG) proteins, the major nonhistone components of chromatin. This hypothesis was based on the fact that rp14.5 is soluble in perchloric acid, a feature of HMG proteins, and copurifies with these proteins when isolated from rodent liver cells (14). However, other features of rp14.5 do not meet the general criteria that characterize the HMG protein family, e.g., bipolar distribution of charged amino acids and monomeric behavior in solution (3). Indeed, biochemical studies have demonstrated that native rp14.5 is able to homodimerize (14). Analysis of the rp14.5 amino acid sequence revealed that the N-terminal half of the molecule has approximately 30% similarity to a domain of the 83- to 90-kDa heat shock protein (hsp) (14), which is highly conserved in lower and higher eukaryotes (1, 8, 9, 24). The prediction that p14.5 is related to hsp's was confirmed in isolated rodent hepatocytes and hepatoma cells, in which the levels of rp14.5 are increased upon heat shock (23). However, there is no evidence that this property is conserved among the other members of the p14.5 family. For instance, the human homologue, hp14.5, in contrast to rp14.5, does not show any amino acid sequence similarity with hsp's (25). A novel biological function of the p14.5 protein family was recently suggested by two independent studies, in which it was shown that p14.5 may be implicated in regulation of protein translation (19, 25). Both the human and the rat p14.5 proteins are able to inhibit cell-free protein synthesis in the rabbit reticulocyte lysate system. Schmiedeknecht et al. have shown that the hp14.5 gene is weakly expressed in freshly isolated monocytes, but high levels of hp14.5 mRNA are detected in monocytes undergoing differentiation (25). Similar results were obtained by immunocytochemical analysis (25). Based on the inhibitory effect of hp14.5 on protein translation and its differentiation-dependent expression, these authors proposed a role of p14.5 in the regulation of protein synthesis during differentiation (25). However, inhibition of protein translation by rp14.5 and hp14.5 in an in vivo model system has not been demonstrated. To clarify the biological function(s) of members of this family, we have characterized the p14.5-related proteins in the budding yeast Saccharomyces cerevisiae. In S. cerevisiae, two members of the p14.5 family have been identified. In the present study, we show that mitochondrial matrix factor 1 (Mmf1p) is a mitochondrial protein, while homologous Mmf1 factor 1 (Hmf1p) is localized in the soluble cytoplasmic fraction. We also show that Mmf1p influences the maintenance of mitochondrial DNA (mtDNA) and the cell division time, while no visible phenotype was observed in Δhmf1 cells. Our data indicate that Mmf1p and Hmf1p have similar biological functions in pathways which are localized in different cellular compartments. Targeting of Hmf1p into mitochondria by fusion to Mmf1p leader peptide is sufficient to rescue the Δmmf1-associated phenotypes. Furthermore, we demonstrate that the yeast and mammalian members of the p14.5 family are functionally related. Our study provides the first in vivo evidence for a biological function of members of this protein family. |
| Databáze: | OpenAIRE |
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