ABC1, a novel yeast nuclear gene has a dual function in mitochondria: it suppresses a cytochrome b mRNA translation defect and is essential for the electron transfer in the bc 1 complex.
We have cloned and sequenced a novel yeast nuclear gene ABC1 which suppresses, in multicopy, the cytochrome b mRNA translation defect due to the nuclear mutation cbs2-223. Analysis of the ABC1 gene shows that it is weakly expressed, it could code for a protein of 501 amino acids which has a typical presequence of a protein imported into mitochondria and which does not display a strong similarity to any known protein. Inactivation of the ABC1 gene is not lethal to the cell but leads to a respiratory defect: no oxygen uptake and no growth on non-fermentable media. A total absence of NADH-cytochrome c oxidoreductase and succinate-cytochrome c oxidoreductase activities concomitant with the presence of specific dehydrogenases, suggests a block in the bc 1 segment of the respiratory chain. However, all the cytochromes are spectrally detectable. Cytochrome b is quite efficiently reduced while cytochromes c1 and c are not. The function of ABC1 in the suppression of a defect in apocytochrome b mRNA translation and in the activity of the bc1 complex suggests that the ABC1 protein would be a novel chaperonin involved both in biogenesis and bioenergetics of mitochondria.
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Centre de Génétique Moléculaire, Laboratoire propre du CNRS associé à l'Université Pierre et Marie Curie, Gif-sur-Yvette, France.
Dujardin
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Slonimski
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D015825:Chromosomes, Fungal; D003573:Cytochrome b Group / Q000235:genetics*; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000378:metabolism; D005800:Genes, Fungal; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
D003573:Cytochrome b Group; D012333:RNA, Messenger; D014450:Electron Transport Complex III