Abstract
The short cytoplasmic peptide segment connecting domains III and IV of voltage-gated sodium channels (III–IV linker) is essential for fast inactivation. To test the functional similarity between the III–IV linker and the potassium channel inactivation particle, we attached the III–IV linker to the amino terminus of a noninactivating potassium channel. This chimeric channel inactivated rapidly and displayed biophysical properties similar to Shaker A-type potassium channels. Recovery from inactivation in the chimeric channels was accelerated by high external potassium, consistent with the idea that potassium ions passing through the channel displaced the III–IV linker inactivation particle. A mutation that completely abolishes fast inactivation in rat brain sodium channels also completely abolished inactivation in the chimera. These results demonstrate that the sodium channel III–IV linker can function as a fast inactivation gate and suggest a functional relationship between the fast inactivation processes of sodium and potassium channels.
Published Version
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