期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：6
页码：2402-2406
DOI：10.1073/pnas.74.6.2402
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Measurements with different chemically modified gramicidins in lipid bilayer membranes were used to discriminate between the dimeric {pi}L,D helix proposed by Urry and the dimeric parallel or antiparallel helices proposed by Veatch and Blout. Evidence for the {pi}L,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 {pi}L,D helices. Dimer formation by head-to-head association of two {pi}L,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 {pi}L,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.
关键词：ionic channels ; gramicidin A analogs ; channel structure
