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Updated: Aug 11, 2026

Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties
10:52

Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties

Published on: October 13, 2010

Comparison of gramicidin A and gramicidin M channel conductance dispersities

J C Markham1, J A Gowen, T A Cross

  • 1Department of Zoology and Center for Neuroscience, Brigham Young University, Provo, UT 84602, USA.

Biochimica Et Biophysica Acta
|July 27, 2001
PubMed

Insights

Gramicidin M (gM) channels, lacking tryptophan, show a distinct secondary conductance band, unlike gramicidin A (gA). This suggests Trp side chains influence gramicidin channel conductance states and stability.

Area of Science:

  • Biophysics
  • Ion Channel Function
  • Molecular Biophysics

Background:

  • Gramicidin A (gA) channels exhibit a primary conductance band with a broad distribution of minor conductance states.
  • Tryptophan (Trp) residues are known to influence the structure and function of gramicidin channels.

Purpose of the Study:

  • To investigate the role of Trp side chains in gramicidin channel conductance dispersity.
  • To compare the conductance properties of gramicidin M (gM) and its enantiomer (gM(-)) with gramicidin A (gA).

Main Methods:

  • Purified gM and gM(-) were reconstituted into lipid bilayers.
  • Channel conductances were measured in various alkali metal solutions, lipid compositions, and detergent conditions.
  • Current-voltage relationships and channel lifetimes were analyzed.

Main Results:

  • gM channels, like gA, display a main conductance band but feature a distinct, narrow secondary band with lower conductance.
  • The secondary conductance peak was prominent in NaCl and KCl but reduced in CsCl and RbCl.
  • Interconversions between primary and lower conductance states were observed, with the secondary state having a shorter mean lifetime.

Conclusions:

  • The absence of Trp side chains in gM leads to a unique secondary conductance state, indicating Trp's role in stabilizing channel conformations.
  • The observed conductance states likely represent variations in peptide or adjacent lipid structure.
  • Alkali metal ion type influences the prominence of the secondary conductance state in gM channels.

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