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  • 1
    Electronic Resource
    Electronic Resource
    Aerolysin, a hemolysin fromAeromonas hydrophila, forms voltage-gated channels in planar lipid bilayers (1990)
    Springer
    The journal of membrane biology 115 (1990), S. 71-81 
    Details
    ISSN: 1432-1424
    Keywords: Aeromonas hydrophila ; aerolysin ; ionic channel ; zinc ions ; voltage dependence ; planar lipid membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The cytolytic toxin aerolysin was found to form ion channels which displayed slight anion selectivity in planar lipid bilayers. In voltage-clamp experiments the ion current flowing through the channels was homogeneous indicating a defined conformation and a uniform size. The channels remained open between −70 to +70 mV, but outside this range they underwent voltage-dependent inactivation which was observed as open-closed fluctuations at the single-channel level. Zinc ions not only prevented the formation of channels by inhibiting oligomerization of monomeric aerolysin but they also induced a closure of preformed channels in a voltage-dependent fashion. The results of a Hill plot indicated that 2–3 zinc ions bound to a site within the channel lumen. Proaerolysin, and a mutant of aerolysin in which histidine 132 was replaced by an asparagine, were both unable to oligomerize and neither could form channels. This is evidence that oligomerization is a necessary step in channel formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869107
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  • 2
    Electronic Resource
    Electronic Resource
    Phallolysin A mushroom toxin, forms proton and voltage gated membrane channels (1985)
    Springer
    European biophysics journal 12 (1985), S. 199-209 
    Details
    ISSN: 1432-1017
    Keywords: Reconstitution ; Amanita phalloides ; mushroom toxin ; ion channel ; lipid dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Phallolysin, a water soluble protein of M r 34,000 produced by the poisonous mushroom Amanita phalloides, causes lysis of various mammalian cell types. Lysis is thought to be initiated by the formation of ion permeable membrane channels. We therefore studied the interaction of phallolysin with solvent-free planar lipid bilayers. In the presence of low phallolysin concentrations (10–100 nM) single channel current fluctuations were observed. Unit channel conductances are 44 pS in 500 mM NaCl and 77 pS in 1 M NaCl. Although the channel does not significantly discriminate between alkali cations, its permeability to Cl- is lower (P K +/P Cl -=4/1). Gating kinetics display a pronounced bursting behavior and a dependence on membrane voltage, cis side pH-value, and on membrane lipid composition. An equivalence relation between membrane voltage and proton concentration was found, i.e. a pH change of one unit is equivalent to a corresponding voltage change of 130 mV. Dependence on the amount of negatively charged lipids is explained by changes of the actual pH due to surface charge effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253846
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  • 3
    Electronic Resource
    Electronic Resource
    Colicin N forms voltage- and pH-dependent channels in planar lipid bilayer membranes (1990)
    Springer
    European biophysics journal 18 (1990), S. 149-158 
    Details
    ISSN: 1432-1017
    Keywords: Colicin N ; Planar lipid bilayers ; Ion channel ; Voltage dependence ; pH-dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The protein antibiotic colicin N forms ion-permeable channels through planar lipid bilayers. Channels are induced when positive voltages higher than +60 mV are applied. Incorporated channels activate and inactivate in a voltage-dependent fashion. It is shown that colicin N undergoes a transition between an “acidic” and a “basic” channel form which are distinguishable by different voltage dependences. The single-channel conductance is non-ohmic and strongly dependent on pH, indicating that titratable groups control the passage of ions through the channel. The ion selectivity of colicin N channels is influenced by the pH and the lipid composition of the bilayer membrane. In neutral membranes the channel undergoes a transition from slightly cation-selective to slightly anion-selective when the pH is changed from 7 to 5. In lipid membranes bearing a negative surface charge the channel shows a more pronounced cation selectivity which decreases but does not reverse upon lowering the pH from 7 to 5. The high degree of similarity between the channel characteristics of colicin A and N suggests that the channels share common features in their molecular structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02427374
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  • 4
    Electronic Resource
    Electronic Resource
    Melittin and a chemically modified trichotoxin form alamethicin-type multi-state pores
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 727 (1983), S. 108-114 
    Details
    ISSN: 0005-2736
    Keywords: Alamethicin ; Ion channel ; Lipid bilayer ; Melittin ; Pore formation ; Trichotoxin ; Voltage-dependent conductance
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(83)90374-7
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  • 5
    Electronic Resource
    Electronic Resource
    Site-directed mutagenesis at histidines of aerolysin from Aeromonas hydrophila: a lipid planar bilayer study (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The role of histidine residues in the formation of channels by the cytolytic toxin aerolysin has been studied in planar lipid bilayers by substituting each of the six histidines in the native protein with asparagine. His341 or His186 mutants had the same channel-forming ability as native toxin, whereas the His332 and His121 mutants were less active. Mutations at His132 and His107, which interfere with the oligomerization of the toxin, drastically reduce pore formation. These findings support the conclusion that oligomerization of the toxin must precede channel formation, and that at least two of the six histidine residues are essential for this to occur. The aerolysin channel is a water-filled pore with an approximate diameter of 9.3 ± 0.4 Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb01983.x
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