Ion transport across a phospholipid membrane mediated by the peptide trichogin GA IV.
Trichogin GA IV is a special member of a class of peptaibols that are linear peptide antibiotics of fungal origin, characterised by the presence of a variable number of alpha-aminoisobutyric acid residues, an acyl group at the N-terminus and a 1,2-amino alcohol at the C-terminus. Most of the peptaibols display ion-channel-forming or at least membrane-modifying properties. The 11-residue-long trichogin GA IV is not only one of shortest peptaibols, but it is also unique for its n-octanoyl group instead of the more common found acetyl group at the N-terminus. For the first time we have found that this lipopeptaibol is able to enhance conduction of monovalent cations through membranes of large unilamellar vesicles (LUVs). The influence of the [Leu-OMe]trichogin GA IV analogue (TRI) on ion permeation was studied under a variety of conditions (lipid composition, lipid-to-peptide ratio and a transmembrane potential). Parallel experiments were performed with the 16-residue long, channel-forming peptaibol, zervamicin (ZER). For the two peptides, the permeability between K(+) and Na(+) was found to be different. In addition, the ion diffusion rate dependencies on the peptide concentration are observed to be different. This might indicate that a different number of aggregated molecules are involved in the rate-limiting step, i.e. 3-4 (TRI) and 4-7 (ZER). In the presence of TRI, dissipation of the transmembrane potential, Delta psi, was observed with a rate to be dependent on the magnitude of both initial Delta psi and peptide concentration. Both peptides were activated by a cis-positive but not by cis-negative Delta psi. Under identical conditions the ion-conducting efficiency of zervamicin was 100-200 times higher than that of trichogin. Our results show that, unlike for zervamicin, the membrane-modifying activity of trichogin is not associated with a channel mechanism.
Kropacheva
T N
TN
Department of Chemistry, Udmurt State University, Izhevsk, Russia.
Raap
J
J
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D006020:Glycopeptides; D017136:Ion Transport; D055666:Lipopeptides; D008563:Membrane Lipids / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides; D010743:Phospholipids / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D055666:Lipopeptides; D008563:Membrane Lipids; D010455:Peptides; D010743:Phospholipids; C116419:trichogin GA IV; D012964:Sodium; D011188:Potassium