ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The conductance of the gramicidin A single channels in glycerolmonooleate membranes is strongly reduced in the presence of Mn2+ 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 Mn2+ ions. Dependence of the nonselective spin-lattice relaxation rates of the gramicidin A protons on Mn2+ concentration was analyzed to determine coordinates of the divalent cation binding sites. It is inferred that Mn2+ 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 Mn2+ 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.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360310408
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