Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 4

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

The access of metabolites into yeast mitochondria in the presence and absence of the voltage dependent anion selective channel (YVDAC1)

100%
Kmita H., Stobienia O., Michejda J.
Acta Biochimica Polonica
|
1999
|
vol. 46
|
issue 4
991-1000
EN
Since yeast Saccharomyces cerevisiae mutants depleted of the voltage dependent anion selective channel (YVDAC1) are still able to grow on a non-fermentable carbon source, a functional transport system in the outer mitochondrial membrane must exist to support the access of metabolites into mitochondria. It was assumed that the properties of the system could be inferred from the differences in the results observed between wild type and mutant mitochondria since no crucial differences in this respect between the two types of mitoplasts were observed. YVDAC1-depleted mitochondria displayed a highly reduced permeability of the outer membrane, which was reflected in increased values of K^{NADH}_{0.5} for respiration and K^{ADP}_{0.5} for triggering phosphorylating state as well as in delayed action of carboxyatractylate (CATR) in inhibition of phosphorylating state. The parameters were chosen to express the accessibility of the applied species to the intermembrane space. The passage of the molecules through the outer membrane depleted of YVDAC1 could be partially improved in the presence of bivalent cations (Mg^{2+}, Ca^{2+}), as in their presence lower values of the calculated parameters were obtained. The restrictions imposed on the transport of molecules through the YVDAC1-depleted outer membrane resulted in a competition between them for the access to the intermembrane space as measured by changes in parameters observed for a given species in the presence of another one. The competition was stronger in the absence of Mg^{2+} and depended on charge and size of transported molecules, as the strongest competitor was CATR and the weakest one - {NADH}. Thus, it can be concluded that the transport system functioning in the absence of YVDAC1 is modulated by bivalent cations and charge as well as size of transported molecules. Since an increased level of respiration due to the dissipation of Δψ causes an increase of K^{NADH}_{0.5} in both wild type and YVDAC1-depleted mitochondria it is concluded that a common property of YVDAC1 and the system functioning in YVDAC1-depleted mitochondria seems to be the dependence of the capacity on the level of mitochondrial respiration.
2
Content available remote

The influence of depletion of voltage dependent anion selective channel on protein import into the yeast Saccharomyces cerevisiae mitochondria.

100%
Szczechowicz A., Hryniewiecka L., Kmita H.
|
2001
|
vol. 48
|
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.
3
Content available remote

Modulation of the voltage-dependent anion-selective channel by cytoplasmic proteins from wild type and the channel depleted cells of Saccharomyces cerevisiae.

100%
Kmita H., Budzińska M., Stobienia O.
|
2003
|
vol. 50
|
issue 2
415-424
EN
It is well known that effective exchange of metabolites between mitochondria and the cytoplasm is essential for cell physiology. The key step of the exchange is transport across the mitochondrial outer membrane, which is supported by the voltage-dependent anion-selective channel (VDAC). Therefore, it is clear that the permeability of VDAC must be regulated to adjust its activity to the actual cell needs. VDAC-modulating activities, often referred to as the VDAC modulator, were identified in the intermembrane space of different organism mitochondria but the responsible protein(s) has not been identified as yet. Because the VDAC modulator was reported to act on VDAC of intact mitochondria when added to the cytoplasmic side it has been speculated that a similar modulating activity might be present in the cytoplasm. To check the speculation we used mitochondria of the yeast Saccharomyces cerevisiae as they constitute a perfect model to study VDAC modulation. The mitochondria contain only a single isoform of VDAC and it is possible to obtain viable mutants devoid of the channel (Δpor1). Moreover, we have recently characterised a VDAC-modulating activity located in the intermembrane space of wild type and Δpor1 S. cerevisiae mitochondria. Here, we report that the cytoplasm of wild type and Δpor1 cells of S. cerevisiae contains a VDAC-modulating activity as measured in a reconstituted system and with intact mitochondria. Since quantitative differences were observed between the modulating fractions isolated from wild type and Δpor1 cells when they were studied with intact wild type mitochondria as well as by protein electrophoresis it might be concluded that VDAC may influence the properties of the involved cytoplasmic proteins. Moreover, the VDAC-modulating activity in the cytoplasm differs distinctly from that reported for the mitochondrial intermembrane space. Nevertheless, both these activities may contribute efficiently to VDAC regulation. Thus, the identification of the proteins is very important.
4
Content available remote

Benzodiazepine binding to mitochondrial membranes of the amoeba Acanthamoeba castellanii and the yeast Saccharomyces cerevisiae.

100%
Slocinska M., Szewczyk A., Hryniewiecka L., Kmita H.
|
|
vol. 51
|
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.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.