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The divalent cation-binding sites of gramicidin A transmembrane ion-channel

✍ Scribed by A. P. Golovanov; I. L. Barsukov; A. S. Arseniev; V. F. Bystrov; S. V. Sukhanov; L. I. Barsukov

Publisher
Wiley (John Wiley & Sons)
Year
1991
Tongue
English
Weight
646 KB
Volume
31
Category
Article
ISSN
0006-3525

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✦ Synopsis

Abstract

The conductance of the gramicidin A single channels in glycerolmonooleate membranes is strongly reduced in the presence of Mn^2+^ cations. The nmr experiments were performed for N‐terminal to N‐terminal gramicidin A dimer formed by two right‐handed single‐stranded helixes incorporated into the sodium dodecyl sulfate micelles in the presence of Mn^2+^ ions. Dependence of the nonselective spin–lattice relaxation rates of the gramicidin A protons on Mn^2+^ concentration was analyzed to determine coordinates of the divalent cation binding sites. It is inferred that Mn^2+^ ions are bound at the channel mouths at distances of 6.4, 8.6, and 8.8 Å (±2 Å) from the oxygen atoms of exposed carbonyl groups of D‐Leu 12, 14, and 10, respectively. The bounded Mn^2+^ retains its hydrate shell, the size of which (≈ 6 Å) exceeds the inner pore diameter (≈ 4 Å). That makes the gramicidin A channel impermeable for divalent cations.

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