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The peptide alamethicin self-assembles to form helix bundle ion channels in membranes. Previous macroscopic measurements have shown that these channels are mildly cation-selective. Models indicate that a source of cation selectivity is a zone of partial negative charge toward the C-terminal end of the peptide. We synthesized an alamethicin derivative with a lysine in this zone (replacing the glutamine at position 18 in the sequence). Microscopic (single-channel) measurements demonstrate that dimeric alamethicin-lysine18 (alm-K18) forms mildly anion-selective channels under conditions where channels formed by the parent peptide are cation-selective. Long-range electrostatic interactions can explain the inversion of ion selectivity and the conductance properties of alamethicin channels.

Original publication

DOI

10.1021/bi9826355

Type

Journal article

Journal

Biochemistry

Publication Date

11/05/1999

Volume

38

Pages

6144 - 6150

Keywords

Alamethicin, Amino Acid Sequence, Anions, Anti-Bacterial Agents, Fees and Charges, Ion Channels, Molecular Sequence Data, Peptide Biosynthesis, Potassium Chloride, Sequence Homology, Amino Acid