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Merck

Gramicidin channels.

IEEE transactions on nanobioscience (2005-04-09)
Olaf S Andersen, Roger E Koeppe, Benoît Roux
ABSTRACT

Gramicidin channels are mini-proteins composed of two tryptophan-rich subunits. The conducting channels are formed by the transbilayer dimerization of nonconducting subunits, which are tied to the bilayer/solution interface through hydrogen bonds between the indole NH groups and the phospholipid backbone and water. The channel structure is known at atomic resolution and the channel's permeability characteristics are particularly well defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the amount of experimental information that is available--for both the wild-type channels and for channels formed by amino acid-substituted gramicidin analogues--gramicidin channels provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For the same reason, gramicidin channels constitute the system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the complex channels formed by integral membrane proteins.

MATERIALS
Product Number
Brand
Product Description

Gramicidin, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Gramicidin from Bacillus aneurinolyticus (Bacillus brevis), Linear polypeptide antibiotic complex. A mixture of gramicidins A, B, C, and D.