The unassigned open reading frame YDL142c was identified to code for cardiolipin synthase, Cls1p. A cls1 deletion strain is viable on glucose, galactose, ethanol, glycerol and lactate containing media, although the growth rate on nonfermentable carbon sources is decreased. Mitochondria of the cls1 mutant are devoid of cardiolipin but accumulate the cardiolipin precursor phosphatidylglycerol when grown on nonfermentable carbon sources. Specific activity of phosphatidylglycerolphosphate synthase in cls1 is reduced to 30^75% of the wildtype level. Amounts of mitochondrial cytochromes and activity of cytochrome c oxidase, however, are not affected in the cls1 deletion strain. Collectively, these data indicate that cardiolipin is not essential for aerobic growth of Saccharomyces cerevisiae.z 1998 Federation of European Biochemical Societies.
Die Bemessung für Querkraft erfolgt heute nach einheitlichen Modellvorstellungen; die Grundlage hierfür wurde vor über 100 Jahren gelegt und ab ca. 1960 durch die Arbeiten auf dem Gebiet der Plastizitätstheorie theoretisch untermauert. In neueren Untersuchungen wurden die Modelle erweitert, wobei die Verträglichkeit der Verformungen und die Bestimmung der effektiven Betondruckfestigkeit im Vordergrund standen. Der vorliegende Beitrag gibt einen Überblick über diese Entwicklungen und zeigt auf, wie die Modelle für die Bemessung und konstruktive Durchbildung verwendet werden können.
We have isolated a yeast nuclear gene that suppresses the previously described respiration-deficient mrs2-1 mutation when present on a multicopy plasmid. Elevated gene dosage of this new gene, termed MRS5, suppresses also the pet phenotype of a mitochondrial splicing-deficient group II intron mutation M1301. The MRS5 gene product, a 13-kDa protein of low abundance, shows no similarity to other known proteins and is associated with the inner mitochondrial membrane, protruding into the intermembrane space. MRS5 codes for an essential protein, as the disruption of this gene is lethal even during growth on fermentable carbon sources. Thus, the Mrs5 protein seems to be involved in mitochondrial key functions aside from oxidative energy conservation, which is dispensable in fermenting yeast cells. Depletion of Mrs5p in yeast cells causes accumulation of unprocessed precursors of the mitochondrial hsp60 protein and defects in all cytochrome complexes. These findings suggest an essential role of Mrs5p in mitochondrial biogenesis.
An in vitro assay was designed to study the import of radiolabeled ergosterol and cholesterol from unilameilar vesicles into isolated mitoehondria of the yeast Saccharomyces cerevisiae.Supply of ergosterol to the mitochondrial surface was enhanced by a cytosolic fraction containing a lipid transfer protein, whereas no such additive to the assay was required for cholesterol transport. Both sterols reached the inner mitochondrial membrane. During import, they were detected in contact sites between the outer and the inner mitochondrial membrane supporting the idea, that these zones are sites of intramitochondrial lipid translocation. Transport of ergosterol between the outer and the inner mitochondrial membrane was not affected by addition of ATP, depletion of ATP caused by treatment of mitochondria with apyrase and oligomycin, and incubation with the uncoupler CCCP, indicating that this process is energy-independent.
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