Voltage-Dependent Gating of Colicin E1 Channels in Planar Bilayers

  • S. L. Slatin
  • K. S. Jakes
  • C. K. Abrams
  • A. Finkelstein
Conference paper
Part of the NATO ASI Series book series (volume 65)

Abstract

The colicins are a group of plasmid-encoded bacteriocins expressed by various strains of E. coli. A subgroup of these toxins, which includes colicins E1, Ia, Ib, B, N, and A, form ion-permeable channels both in the inner membrane of the target bacterium and in lipid bilayer membranes (for reviews, see Slatin, 1988; Pattus et al., 1990; Cramer et al., 1990). Each of these channel-forming toxins consists of a single polypeptide chain of between 500 and 600 amino acids, with a single hydrophobic segment near the C-terminus (residues 474–508 in El). For colicins El and A, it has been shown explicitly that only the carboxyl terminal third of the protein is required for channel formation. The addition of colicin El in nanomolar concentrations to the bathing solution on one side of a planar lipid bilayer (the eis side) induces a large, voltage-dependent conductance attributable to the gating of colicin channels. Cis positive voltages (all voltages refer to thecis compartment with respect to the trans, which is always at zero potential) tend to open channels, whereas cis negative potentials close them. The rate at which channels open and close is highly voltage dependent. Gating is faster at large absolute voltages than at voltages near zero. The rates are also pH dependent -- increasing the pH of the cis solution from 3.5 dramatically decreases the turn-on rate, whereas raising the trans pH dramatically decreases the turn-off rate.

Keywords

Amide Propane Cysteine Carboxyl Polypeptide 

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References

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Copyright information

© Springer-Verlag Berlin Heidelberg 1992

Authors and Affiliations

  • S. L. Slatin
    • 1
  • K. S. Jakes
    • 1
  • C. K. Abrams
    • 1
  • A. Finkelstein
    • 1
  1. 1.Department of Physiology and BiophysicsAlbert Einstein College of MedicineBronxUSA

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