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. 1977 Jun;74(6):2402–2406. doi: 10.1073/pnas.74.6.2402

Structure of the gramicidin A channel: Discrimination between the πL,D and the β helix by electrical measurements with lipid bilayer membranes

E Bamberg 1, H J Apell 1, H Alpes 1
PMCID: PMC432180  PMID: 70038

Abstract

Measurements with different chemically modified gramicidins in lipid bilayer membranes were used to discriminate between the dimeric πL,D helix proposed by Urry and the dimeric parallel or antiparallel helices proposed by Veatch and Blout. Evidence for the πL,D helix was obtained on the basis of the different actions of a negatively charged O-pyromellitylgramicidin and a negatively charged N-pyromellityldesformylgramicidin on lipid bilayer membranes. O-Pyromellitylgramicidin forms ionic channels in lipid membranes when it is applied to both sides of the membrane. In contrast to unmodified gramicidin, O-pyromellitylgramicidin is inactive when it is applied only to one side of the membrane. N-Pyromellityldesformylgramicidin does not form ionic channels in lipid bilayer membranes whether it is applied to one or both sides of the membrane. These results support the view that the gramicidin channel is formed by two πL,D helices. Dimer formation by head-to-head association of two πL,D helices needs six intermolecular hydrogen bonds, which are located at the formyl end of the molecule and which occur deep within the lipid membrane. In the head-to-head associated πL,D helix the absence of the formyl group leads to an inactivation of the peptide, whereas in a parallel or antiparallel double-stranded helix the absence of the formyl group should have only minor effects.

Keywords: ionic channels, gramicidin A analogs, channel structure

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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