Voltage-Dependent Gating of an Asymmetric Gramicidin Channel
by Oiki, Shigetoshi; Koeppe II, R. Erdman; Andersen, Olaf S.
In an effort to understand the molecular mechanisms of voltage activation of ion channels, we have chosen a system of known structure and examined the properties of heterodimeric channels formed between [Val(1)]gramicidin A ([Val(1)]gA) and [F(6)Val(1)]gramicidin A ([F(6)Val(1)]gA). Gramicidin channels are usually not voltage-dependent; but the introduction of a single symmetrybreaking dipolar F(6)Val(1) residue into a ([Val(1)]gA)(2) dimer to form the [F(6)Val(1)]gA/[Val(1)]gA heterodimer induces voltage-dependent transitions between two conducting states: a high-conductance state and a zero conductance (closed) state. The distribution between these states varies as a function of the applied potential but is not dependent on the nature of the permeant ion (H+ or Cs+). The permeating ions do not seem to contribute to the apparent gating charge.
- Proceedings of the National Academy of Sciences of the United States of America
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