Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    A non-equilibrium thermodynamics model of reconstituted Ca2+-ATPase (1998)
    Springer
    European biophysics journal 27 (1998), S. 255-262 
    Details
    ISSN: 1432-1017
    Keywords: Key words Coupling stoichiometry ; Electrogenicity ; Slip ; Calcium pumping ; Proton ejection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A non-equilibrium thermodynamics (NET) model describing the action of completely coupled or `slipping' reconstituted Ca2+-ATPase is presented. Variation of the coupling stoichiometries with the magnitude of the electrochemical gradients, as the ATPase hydrolyzes ATP, is an indication of molecular slip. However, the Ca2+ and H+ membrane-leak conductances may also be a function of their respective gradients. Such non-ohmic leak typically yields `flow-force' relationships that are similar to those that are obtained when the pump slips; hence, caution needs to be exercised when interpreting data of Ca2+-ATPase-mediated fluxes that display a non-linear dependence on the electrochemical proton (Δµ˜H) and/or calcium gradients (Δµ˜Ca). To address this issue, three experimentally verifiable relationships differentiating between membrane leak and enzymic slip were derived. First, by measuring Δµ˜H as a function of the rate of ATP hydrolysis by the enzyme. Second, by measuring the overall `efficiency' of the pump as a function of Δµ˜H. Third, by measuring the proton ejection rate by the pump as a function of its ATP hydrolysis rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050132
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Sustained oscillations in free-energy state and hexose phosphates in yeast (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 731-740 
    Details
    ISSN: 0749-503X
    Keywords: oscillation ; glycolysis ; yeast ; Saccharomyces cerevisiae ; intracellular metabolites ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In a population of intact cells of the yeast Saccharomyces cerevisiae the dynamics of glycolytic metabolism were investigated under the condition of sustained oscillations. At 5-s intervals cells were quenched in -40°C methanol, extracted and the intracellular concentrations of glycolytic metabolites, adenine nucleotides and phosphate were analysed. Oscillations were found for the glycolytic intermediates glucose 6-phosphate, fructose 6-phosphate and fructose 1,6-bisphosphate. At variance with earlier reports on transient glycolytic oscillations, some intermediates further down the glycolytic pathway did not oscillate significantly, even though NADH did. In addition, the adenylate energy charge and the free energy of ATP hydrolysis oscillated significantly. Dynamic coupling through the latter may be responsible for this effective compartmentation of glycolytic dynamics.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    High-affinity glucose uptake in Saccharomyces cerevisiae is not dependent on the presence of glucose-phosphorylating enzymes (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 439-447 
    Details
    ISSN: 0749-503X
    Keywords: transport ; glucose uptake ; Saccharomyces cerevisiae ; yeast ; rapid kinetics ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Glucose uptake in Saccharomyces cerevisiae is believed to consist of two kinetically distinguishable components, the affinity of which is modulated during growth on glucose. It has been reported that triple hexose-kinase deletion mutants do not exhibit high-affinity glucose uptake. This raises the question of whether and how high-affinity glucose uptake is related to the presence of glucose-phosphorylating enzymes. In this study the kinetics of glucose uptake in both wild-type cells and cells of hexose-kinase deletion mutants, grown on either glycerol or galactose, were determined using a rapid-uptake method. In wild-type cells glucose uptake measured over either 5 s or 200 ms exhibited high affinity. In contrast, in cells of hexose-kinase deletion mutants the apparent affinity of glucose uptake was dependent on the time scale during which uptake was measured. Measurements on the 5-s scale showed apparent low-affinity uptake whereas measurements on the 200-ms scale showed high-affinity uptake. The affinity and maximal rate of the latter were comparable to those in wild-type cells.Using a simple model for a symmetrical facilitator, it was possible to simulate the experimentally determined relation between apparent affinity and the time scale used.The results suggest that high-affinity glucose transport is not necessarily dependent on the presence of glucose-phosphorylating enzymes. Apparent low-affinity uptake kinetics can arise as a consequence of an insufficient rate of removal of intracellular free glucose by phosphorylation.This study underlines the need to differentiate between influences of the translocator and of metabolism on the apparent kinetics of sugar uptake in yeast.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...