When present in micromolar amounts on one side of phospholipid bilayer membranes, monazomycin (a positively charged, polyene-like antibiotic) induces dramatic voltage-dependent conductance effects. Voltage clamp records are very similar in shape to those obtained from the potassium conductance system of the squid axon. The steady-state conductance is proportional to the 5th power of the monazomycin concentration and increases exponentially with positive voltage (monazomycin side positive); there is an e-fold change in conductance per 4–6 mv. The major current-carrying ions are univalent cations. For a lipid having no net charge, steady-state conductance increases linearly with KCl (or NaCl) concentration and is unaffected by Ca++ or Mg++. The current-voltage characteristic which is normally monotonic in symmetrical salt solutions is converted by a salt gradient to one with a negative slope-conductance region, although the conductance-voltage characteristic is unaffected. A membrane treated with both monazomycin and the polyene antibiotic nystatin (which alone creates anion-selective channels) displays bistability in the presence of a salt gradient. Thus monazomycin and nystatin channels can exist in parallel. We believe that many monazomycin monomers (within the membrane) cooperate to form a multimolecular conductance channel; the voltage control of conductance arises from the electric field driving monazomycin molecules at the membrane surface into the membrane and thus affecting the number of channels that are formed.
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1 September 1972
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September 01 1972
Voltage-Dependent Conductance Induced in Thin Lipid Membranes by Monazomycin
Robert U. Muller,
Robert U. Muller
From the Departments of Physiology and Neurology, Albert Einstein College of Medicine, Bronx, New York 10461
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Alan Finkelstein
Alan Finkelstein
From the Departments of Physiology and Neurology, Albert Einstein College of Medicine, Bronx, New York 10461
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Robert U. Muller
From the Departments of Physiology and Neurology, Albert Einstein College of Medicine, Bronx, New York 10461
Alan Finkelstein
From the Departments of Physiology and Neurology, Albert Einstein College of Medicine, Bronx, New York 10461
Received:
March 06 1972
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright © 1972 by The Rockefeller University Press
1972
J Gen Physiol (1972) 60 (3): 263–284.
Article history
Received:
March 06 1972
Citation
Robert U. Muller, Alan Finkelstein; Voltage-Dependent Conductance Induced in Thin Lipid Membranes by Monazomycin . J Gen Physiol 1 September 1972; 60 (3): 263–284. doi: https://doi.org/10.1085/jgp.60.3.263
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Monazomycin-induced single channels. I. Characterization of the elementary conductance events.
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