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  • Staphylococcus aureus  (2)
  • membrane potential  (2)
  • Channel size  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 12 (1985), S. 229-235 
    ISSN: 1432-1017
    Keywords: Lymphocytes ; Lettré cells ; membrane potential ; Na+ pump ; cation diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Lettré cells maintain a plasma membrane potential near — 60mV, yet are scarcely depolarized by 80 mM Rb+ and are relatively impermeable to 86Rb+. They are depolarized by ouabain without a concomitant change in intracellular cation content. Addition of K+ to cells suspended in a K+ free medium, or of Na+ to cells in a Na+ free medium, hyperpolarizes the cells. They contain electroneutral transport mechanisms for Na+, K+ and H+ which can function as Na+:K+ and Na+:H+ exchanges. It is concluded that plasma membrane potential of Lettré cells, in steady-state for Na+ and K+, is produced by an electrogenic Na+ pump sustained by electroneutral exchanges, and restricted by anion leakage.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1424
    Keywords: Alpha toxin ; Ion channel ; Lettre cell ; Patch clamp ; Planar bilayer ; Staphylococcus aureus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The conductance of pores induced by Staphylococcus aureus α-toxin in Lettre cells has been compared to that in bilayers composed of synthetic lipids or Lettre cell membrane constituents. Previously described characteristics of toxin-induced conductance changes in lipid bilayers, namely rectification, voltage-dependent closure, and closure at low pH or in the presence of divalent cations (Menestrina, 1986) are displayed also in bilayers prepared from Lettre cell membranes and in patch clamped Lettre cells. It is concluded that endogenous proteins do not affect the properties of α-toxininduced channels significantly and that the relative lack of ion channels in Lettre cells makes them ideal for studies of pore-forming toxins by the patch clamp technique.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 79 (1984), S. 275-284 
    ISSN: 1432-1424
    Keywords: oxonol-V ; membrane potential ; ion pumps ; Lettré cell ; organic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The plasma membrane potential of Lettré cells has been determined with the optical indicator oxonol-V and found to be −57 mV at 37°C (range −20 to −80 mV depending on the physiological condition of the cells). Increasing extracellular K+ does not depolarize cells: even in the presence of 155mM K+ the potential is −41 mV; membrane potential is also insensitive to the chemical gradient of Na+,Mg2+, Ca2+ or Cl−. Ouabain depolarizes the cells; H+ efflux from cells is stimulated by extracellular Na+. We propose that in Lettré cells the plasma membrane potential is generated by electrogenic cation pumps. The balancing fluxes of Na+ and K+ are mainly through electroneutral cation exchanges (Na+/K+ and Na+/H+) and the magnitude of the potential is limited by organic anion leaks. Such a mechanism may operate in other biological membranes also.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 147 (1995), S. 233-239 
    ISSN: 1432-1424
    Keywords: Alpha toxin ; Channel size ; Conductance states ; Planar bilayer ; Polymer exclusion ; Staphylococcus aureus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We have used a polymer-exclusion method to estimate the sizes of the high and low-conductance states of Staphylococcus aureus α-toxin channels across planar lipid bilayers. Despite a 〉10-fold difference in conductance between high and low-conductance states, the size differs by 〈2-fold. We conclude that factors other than the dimensions have a strong influence on the conductance of α-toxin channels. We also show that the high conductance state is destabilized by the presence of high molecular weight polymers outside the channel, compatible with the removal of channel water as the high conductance state “shrinks” to the low conductance state.
    Type of Medium: Electronic Resource
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