Intrinsic rectification of ion flux in alamethicin channels: studies with an alamethicin dimer

Abstract

Covalent dimers of alamethicin form conducting structures with gating properties that permit measurement of current-voltage (I-V) relationships during the lifetime of a single channel. These I-V curves demonstrate that the alamethicin channel is a rectifier that passes current preferentially, with voltages of the same sign as that of the voltage that induced opening of the channel. The degree of rectification depends on the salt concentration; single-channel I-V relationships become almost linear in 3 M potassium chloride. These properties may be qualitatively understood by using Poisson-Nernst-Planck theory and a modeled structure of the alamethicin pore.

Molecular dynamics simulations of antimicrobial peptides: From membrane binding to trans‐membrane channels

“…A special property of alamethicin is that it forms ion channels with well-defined and reproducible conductance levels, thought to correspond to bundles formed by different numbers of helices (the barrel-stave model). Synthetic analogues have been synthesized that contain covalently linked helices, supporting the barrel stave model [23,24].…”

“…[28,29], the properties of a single alamethicin helix [30 -36], lipid-peptide interactions [33,37], and the interpretation of conductance data of synthetic analogues of alamethicin [23,24]. Shown in Figure 2 are a number of starting structures for simulations of alamethicin in different environments.…”

Radio-frequency response of single pores and artificial ion channels

“…The junctions' I V characteristic has to be nonlinear of some form, which is the result of asymmetric barrier resistances and capacitances such as in a Schottky diode. In dc measurements on ALA it was shown by Woolley et al [14] that the I V relation of ALA is non-ohmic due to the electrostatic potential profile within this ion channel. This is also termed 'rectification'.…”

Channel‐Forming Activity of Alamethicin: Effects of Covalent Tethering

“…A parallel arrangement of helices is also supported by the observed asymmetry of current/voltage curves (see discussion below) [2] [4] [23].…”

“…The lack of conductance in KCl may suggest that the tetramer is, in fact, non-conducting or that the porphyrin template severely inhibits access by KCl. single-channel current/voltage curves to be recorded for the first time [21] [23]. These data, together with modeling and simulation work, can provide detailed information about the permeation properties of alamethicin channels and the molecular features of the peptides that control these properties.…”