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1
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Regulation of electron flux in the branched respiratory chain in mitochondria of Acanthamoeba castellanii

100%
Jarmuszkiewiez W., Hryniewiecka L.
Acta Biochimica Polonica
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1994
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vol. 41
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issue 2
218-220
2
Content available remote

Effect of growth at low temperature on the alternative pathway respiration in Acanthamoeba castellanii mitochondria.

81%
Jarmuszkiewicz W., Frączyk O., Hryniewiecka L.
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2001
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vol. 48
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issue 3
729-737
EN
Mitochondria of amoeba Acanthamoeba castellanii in addition to the conventional cytochrome pathway possess, like plant mitochondria, a cyanide-resistant alternative quinol oxidase. In mitochondria isolated from amoeba batch culture grown temporarily at low temperature (6°C), higher respiration was accompanied by lower coupling parameters as compared to control culture (grown at 28°C). In the presence of benzohydroxamate, respiratory rates and coupling parameters were similar in both types of mitochondria indicating that growth in cold conditions did not disturb the cytochrome pathway. Increased contribution of alternative oxidase in total mitochondrial respiration in low-temperature-grown amoeba cells was confirmed by calculation of its contribution using ADP/O measurements. Furthermore, in mitochondria from low-temperature- grown cells the content of the alternative oxidase was increased and correlated with the increase in the unstimulated and GMP-stimulated cyanide-resistant respiratory activity. A possible physiological role of higher activity of alternative oxidase as response to growth at a low temperature in unicellular organisms, such as amoeba, is discussed.
3
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The influence of depletion of voltage dependent anion selective channel on protein import into the yeast Saccharomyces cerevisiae mitochondria.

81%
Szczechowicz A., Hryniewiecka L., Kmita H.
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2001
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vol. 48
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issue 3
719-728
EN
The supply of substrates to the respiratory chain as well as of other metabolites (e.g. ATP) into inner compartments of mitochondria is crucial to preprotein import into these organelles. Transport of the compounds across the outer mitochondrial membrane is enabled by mitochondrial porin, also known as the voltage-dependent anion-selective channel (VDAC). Our previous studies led to the conclusion that the transport of metabolites through the outer membrane of the yeast Saccharomyces cerevisiae mitochondria missing VDAC (now termed YVDAC1) is considerably restricted. Therefore we expected that depletion of YVDAC1 should also hamper protein import into the mutant mitochondria. We report here that YVDAC1-depleted mitochondria are able to import a fusion protein termed pSu9-DHFR in the amount comparable to that of wild type mitochondria, although over a considerably longer time. The rate of import of the fusion protein into YVDAC1-depleted mitochondria is distinctly lower than into wild type mitochondria probably due to restricted ATP access to the intermembrane space and is additionally influenced by the way the supporting respiratory substrates are transported through the outer membrane. In the presence of ethanol, diffusing freely through lipid membranes, YVDAC1-depleted mitochondria are able to import the fusion protein at a higher rate than in the presence of external NADH which is, like ATP, transported through the outer membrane by facilitated diffusion. It has been shown that transport of external NADH across the outer membrane of YVDAC1-depleted mitochondria is supported by the protein import machinery, i.e. the TOM complex (Kmita & Budzińska, 2000, Biochim. Biophys. Acta 1509, 86-94.). Since the TOM complex might also contribute to the permeability of the membrane to ATP, it seems possible that external NADH and ATP as well as the imported preprotein could compete with one another for the passage through the outer membrane in YVDAC1-depleted mitochondria.
4
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Benzodiazepine binding to mitochondrial membranes of the amoeba Acanthamoeba castellanii and the yeast Saccharomyces cerevisiae.

81%
Slocinska M., Szewczyk A., Hryniewiecka L., Kmita H.
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vol. 51
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issue 4
953-962
EN
Benzodiazepine binding sites were studied in mitochondria of unicellular eukaryotes, the amoeba Acathamoeba castellanii and the yeast Saccharomyces cerevisiae, and also in rat liver mitochondria as a control. For that purpose we applied Ro5-4864, a well-known ligand of the mitochondrial benzodiazepine receptor (MBR) present in mammalian mitochondria. The levels of specific [3H]Ro5-4864 binding, the dissociation constant (KD) and the number of [3H]Ro5-4864 binding sites (Bmax) determined for fractions of the studied mitochondria indicate the presence of specific [3H]Ro5-4864 binding sites in the outer membrane of yeast and amoeba mitochondria as well as in yeast mitoplasts. Thus, A. castellanii and S. cerevisiae mitochondria, like rat liver mitochondria, contain proteins able to bind specifically [3H]Ro5-4864. Labeling of amoeba, yeast and rat liver mitochondria with [3H]Ro5-4864 revealed proteins identified as the voltage dependent anion selective channel (VDAC) in the outer membrane and adenine nucleotide translocase (ANT) in the inner membrane. Therefore, the specific MBR ligand binding is not confined only to mammalian mitochondria and is more widespread within the eukaryotic world. However, it can not be excluded that MBR ligand binding sites are exploited efficiently only by higher multicellular eukaryotes. Nevertheless, the MBR ligand binding sites in mitochondria of lower eukaryotes can be applied as useful models in studies on mammalian MBR.
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