alamethicin and peptaibolin

Peptaibols are membrane-active polypeptides isolated from fungal sources. They are characterized by the presence of an unusual amino acid, alpha-aminoisobutyric acid, and a C-terminal hydroxylated amino acid. Peptaibols exhibit antibiotic activity against bacteria and fungi. Their amphipathic nature allows them to self-associate into oligomeric ion-channel assemblies which span the width of lipid bilayer membranes. Over 200 peptaibol sequences have been reported to date, which are compiled in the Peptaibol Database at http://www.cryst.bbk.ac.uk/peptaibol. Alignments of these sequences have been carried out in order to define a series of related subfamilies (SFs) with common sequence features thought to be important for channel formation. Crystal structures determined for a number of peptaibols from the various SFs provide the bases both for modelling of the channel structures and for modelling structures of other members of the same SFs.

Topics: Alamethicin; Amino Acid Sequence; Anti-Bacterial Agents; Conserved Sequence; Crystallography, X-Ray; Ion Channels; Models, Biological; Peptaibols; Peptides; Sequence Alignment

Extraction followed by reverse phase liquid chromatography (LC)/electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS) analysis has been successfully developed for the determination of peptaibols, fungal toxic metabolites, in marine sediments. Spiking experiments showed that the mean recovery of target compounds exceeded 85% at a spiking level of 10 ng/g of sediment (wet weight). Detection and quantification limits were 250 and 830 pg/g of sediment, respectively. The method developed constituted the first sensitive assay for quantification of peptaibol trace amounts in a natural environment. A concentration of 5 ng/g in sediment samples collected from Fier d'Ars was found.

Topics: Alamethicin; Calibration; Chromatography, Liquid; Complex Mixtures; Environment; Geologic Sediments; Peptaibols; Peptides; Reproducibility of Results; Solvents; Spectrometry, Mass, Electrospray Ionization

The effect of a transmembrane potential on ion channel formation by zervamicin II (ZER-II) was studied in a vesicular model system. The dissipation of diffusion potential caused by addition of ZER-II to small phosphatidylcholine vesicles was monitored using fluorescent (Safranine T) and optical (Oxonol YI) probes. Cis-positive potentials facilitated channel formation, while at cis-negative potentials, ion fluxes were inhibited. A potential-independent behavior of ZER-II was observed at high peptide concentrations, most likely due to its membrane modifying property.

Topics: Alamethicin; Amino Acid Sequence; Anti-Bacterial Agents; Electric Conductivity; Ion Channels; Membrane Potentials; Molecular Sequence Data; Peptaibols; Peptides; Phospholipids; Valinomycin