Formation of ion channels in lipid bilayers by a peptide with the predicted transmembrane sequence of botulinum neurotoxin A.
Synthetic peptides patterned after the predicted transmembrane sequence of botulinum toxin A were used as tools to identify an ion channel-forming motif. A peptide denoted BoTxATM, with the sequence GAVILLEFIPEIAI PVLGTFALV, forms cation-selective channels when reconstituted in planar lipid bilayers. As predicted, the self-assembled conductive oligomers express heterogeneous single-channel conductances. The most frequent openings exhibit single-channel conductance of 12 and 7 pS in 0.5 M NaCl, and 29 and 9 pS in 0.5 M KCl. In contrast, ion channels are not formed by a peptide of the same amino acid composition as BoTxATM with a scrambled sequence. Conformational energy calculations show that a bundle of four amphipathic alpha-helices is a plausible structural motif underlying the measured pore properties. These studies suggest that the identified module may play a functional role in the ion channel-forming activity of intact botulinum toxin A.
Department of Biology, University of California San Diego, La Jolla 92093-0366, USA.
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Oblatt-Montal
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Yamazaki
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Nelson
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Montal
D000595:Amino Acid Sequence; D001905:Botulinum Toxins / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels; D008051:Lipid Bilayers; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013744:Tetanus Toxin / Q000737:chemistry
D007473:Ion Channels; D008051:Lipid Bilayers; D013744:Tetanus Toxin; D001905:Botulinum Toxins