Abstract
Peptaibols are considered as models of those ion channels which consist of a bundle of transbilayer helices surrounding a central pore. X-Ray diffraction and NMR studies have yielded high resolution structures for several peptaibols. In conjunction with other spectroscopic investigations and molecular dynamics simulations, these studies suggest that peptaibols form proline-kinked α-helices, and that there may be “hinge-bending” movement of the helix in the region of the central proline residue. The amphipathicity of peptaibol helices is analyzed in relation to their channel-forming properties. Studies of the interactions of peptaibols with lipid bilayers suggest that they are helical when in a membrane-like environment, and that the helix orientation relative to the bilayer is sensitive to the peptaibol: lipid ratio, and to the degree of hydration of the bilayer. Electrical studies reveal that many peptaibols form multiple-conductance level channels in a voltage-dependent fashion. Analysis of conductance levels provides support for the “barrel stave” model of channel formation, whereby different conductance levels correspond to different numbers of monomers in a helix bundle. Alternative models for voltage-activation are discussed, and the roles of molecular dipoles and of hinge-bending in this process are considered. Two molecular models for an N = 6 bundle of alamethicin helices are presented and their electrostatic properties analyzed. The relevance of studies of peptaibols to channel and transport proteins in general is considered.
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Abbreviations
- Aib:
-
α-amino-isobutyric acid
- Alm:
-
alamethicin
- ATR-FTIR:
-
attenuated total reflection Fourier transform infrared
- CD:
-
circular dichroism
- CFP:
-
channel-forming peptide
- Chol:
-
cholesterol
- diPhyPC:
-
diphytanoyl phosphatidylcholine
- DMPC:
-
dimyristoyl phosphatidylcholine
- DOPC:
-
dioleoyl phosphatidylcholine
- DOPE:
-
dioleoyl phosphatidylethanolamine
- DPPS:
-
dipahnitoyl phosphatidylserine
- DTPC:
-
ditetradecyl phosphatidylcholine
- HSM:
-
hydrophilic surface map
- I-V:
-
current-voltage
- MLV:
-
multilamellar vesicle
- nAChR:
-
nicotinic acetylcholine receptor
- P:L:
-
protein-to-lipid ratio
- POPC:
-
palmitoyloleoyl phosphatidylcholine
- SUV:
-
small unilamellar vesicle
- Zrv:
-
zervamicin
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Sansom, M.S.P. Alamethicin and related peptaibols — model ion channels. Eur Biophys J 22, 105–124 (1993). https://doi.org/10.1007/BF00196915
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DOI: https://doi.org/10.1007/BF00196915