Guanidinium as a Probe of the Gramicidin Channel Interior

  • David Busath
  • Greg Hemsley
  • Terry Bridal
  • Michael Pear
  • Kevin Gaffney
  • Martin Karplus
Conference paper
Part of the The Jerusalem Symposia on Quantum Chemistry and Biochemistry book series (JSQC, volume 21)

Abstract

Guanidinium is a planar trigonal cation which is similar in size to the gramicidin channel pore. We measured the effect of guanidinium on the conductance properties of the gramicidin channel and theoretically evaluated its interactions with the β-6.3 channel interior using an energy minimization and conformational search approach. Guanidinium current (measured in the absence of other permeable ions) could not be detected directly (g(Guan)/g(K) < 0.004). However, guanidinium induces blocks in gramicidin channel potassium currents. The average block duration gets shorter with increased membrane potential suggesting that guanidinium can penetrate the ion channel. Energy minimization calculations indicate that, by reorienting along the pathway, the guanidinium should be able to penetrate the gramicidin channel. This finding is illustrated by a computer graphics animation of the series of minimum-energy orientations. The low permeability of the channel to guanidinium is tentatively ascribed to an entropic barrier resulting from the restrictions on the ion motion in the channel.

Keywords

Outward Current Selectivity Filter Guanidine Hydrochloride Free Energy Barrier Transmembrane Channel 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Kluwer Academic Publishers 1988

Authors and Affiliations

  • David Busath
    • 1
  • Greg Hemsley
    • 1
  • Terry Bridal
    • 1
  • Michael Pear
    • 1
  • Kevin Gaffney
    • 2
  • Martin Karplus
    • 2
  1. 1.Section of Physiology and BiophysicsBrown UniversityProvidenceUSA
  2. 2.Department of ChemistryHarvard UniversityCambridgeUSA

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