Publicação
Studies on the metabolic role of the mitochondrial electron transfer proteins ETF and ETFDH in Saccharomyces cerevisiae
| Resumo: | The ETF (electron transfer flavoprotein) and ETFDH (ETF dehydrogenase) are flavoproteins involved in electron transfer from primary acyl-CoA dehydrogenases to ubiquinone of the mitochondrial electron transport system (ETS). ETF is a heterodimer composed of subunits ETFα and ETFβand ETFDH is associated to the mitochondrial inner membrane. Electron-donor metabolic reactions in which primary acyl-CoA dehydrogenases are known to catalyze reactions are β-oxidation, amino acid catabolism, choline catabolism and sarcosine and dimethylglycine catabolism. In mammalian cells, β-oxidation takes place in both mitochondria and peroxisomes, depending on fatty acid length and double bonds. For other eukaryotic organisms, it is exclusively peroxisomal and, hence, not directly coupled to ATP generation. The Saccharomyces cerevisiae orthologues of ETF and ETFDH are encoded by YPR004c (ETFα), YGR207c (ETFβ) and YOR356w (ETFDH) and have been demonstrated to be mitochondrial proteins. In this work, we aim at elucidate the role of ETF and ETFDH in yeast by exploring the possibility of involvement in the catabolism of amino acids, choline, sarcosine and dimethylglycine; in oxidative stress; and in heat shock. Mutant strains affected in these genes were tested for growth on media with different carbon sources. All mutant strains displayed normal growth when compared with their parental on glucose and on non-fermentable carbon sources: ethanol, glycerol, succinate, malate, pyruvate and lactate. Growth on palmitic acid, a saturated fatty acid acid with 16 carbons, was unaffected by these mutations as well. However, when the monounsaturated fatty acid oleic acid (18:1 cis-9) was used as sole carbon and energy source, the mutant strains showed growth deficiency. Considering that beta-oxidation in yeasts is exclusively peroxisomal, this unexpected result suggests an involvement of ETF and ETFDH on metabolism of unsaturated fatty acids. This implication will be further investigated by testing other fatty acids with more double bonds and with branched chains to explore possible alternative catabolic reactions that might occur in the mitochondrion. Furthermore, the involvement in catabolism of nitrogen-containing compounds (amino acids, choline, sarcosine and dimethylglycine) will be assayed as well. Recent evidence from global transcription analysis indicates an activation of expression of YPR004c and YGR207c under oxidative stress by hydrogen peroxide and menadione and an activation of YGR207c and YOR356w by heat shock. These conditions will be investigated for fitness with the corresponding mutant strains. |
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| Autores principais: | Rodrigues, Aurora |
| Outros Autores: | Vasconcelos, Filipe; Oliveira, Rui Pedro Soares de |
| Assunto: | Saccharomyces cerevisiae Mitochondria Electron transfer flavoproteins |
| Ano: | 2007 |
| País: | Portugal |
| Tipo de documento: | póster em conferência |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The ETF (electron transfer flavoprotein) and ETFDH (ETF dehydrogenase) are flavoproteins involved in electron transfer from primary acyl-CoA dehydrogenases to ubiquinone of the mitochondrial electron transport system (ETS). ETF is a heterodimer composed of subunits ETFα and ETFβand ETFDH is associated to the mitochondrial inner membrane. Electron-donor metabolic reactions in which primary acyl-CoA dehydrogenases are known to catalyze reactions are β-oxidation, amino acid catabolism, choline catabolism and sarcosine and dimethylglycine catabolism. In mammalian cells, β-oxidation takes place in both mitochondria and peroxisomes, depending on fatty acid length and double bonds. For other eukaryotic organisms, it is exclusively peroxisomal and, hence, not directly coupled to ATP generation. The Saccharomyces cerevisiae orthologues of ETF and ETFDH are encoded by YPR004c (ETFα), YGR207c (ETFβ) and YOR356w (ETFDH) and have been demonstrated to be mitochondrial proteins. In this work, we aim at elucidate the role of ETF and ETFDH in yeast by exploring the possibility of involvement in the catabolism of amino acids, choline, sarcosine and dimethylglycine; in oxidative stress; and in heat shock. Mutant strains affected in these genes were tested for growth on media with different carbon sources. All mutant strains displayed normal growth when compared with their parental on glucose and on non-fermentable carbon sources: ethanol, glycerol, succinate, malate, pyruvate and lactate. Growth on palmitic acid, a saturated fatty acid acid with 16 carbons, was unaffected by these mutations as well. However, when the monounsaturated fatty acid oleic acid (18:1 cis-9) was used as sole carbon and energy source, the mutant strains showed growth deficiency. Considering that beta-oxidation in yeasts is exclusively peroxisomal, this unexpected result suggests an involvement of ETF and ETFDH on metabolism of unsaturated fatty acids. This implication will be further investigated by testing other fatty acids with more double bonds and with branched chains to explore possible alternative catabolic reactions that might occur in the mitochondrion. Furthermore, the involvement in catabolism of nitrogen-containing compounds (amino acids, choline, sarcosine and dimethylglycine) will be assayed as well. Recent evidence from global transcription analysis indicates an activation of expression of YPR004c and YGR207c under oxidative stress by hydrogen peroxide and menadione and an activation of YGR207c and YOR356w by heat shock. These conditions will be investigated for fitness with the corresponding mutant strains. |
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