Читать книгу Neurology - Charles H. Clarke - Страница 88

Voltage‐gated potassium channels are the largest family. They are composed of four homologous pore‐forming subunits, and four intracellular beta subunits. They contribute to regulation of excitability and termination of action potentials. Each subunit of a voltage‐gated potassium channel typically contains six transmembrane α‐helices, of which the S4 segment acts as a voltage sensor. Such channels open in variable ways upon membrane depolarisation.

By contrast, the pore‐forming subunits of inward‐rectifying potassium channels lack the voltage‐sensing module S4. These channels conduct potassium ions preferentially at negative potentials and have an important role: they stabilise membrane potentials at rest.

Dominantly inherited loss‐of‐function mutations of KCNA1, that encodes the Kv1.1 potassium channel, cause episodic ataxia type 1, characterised by paroxysms of dyskinesia and neuromyotonia.

Some gain‐of‐function mutations of a calcium gated potassium channel (KCNMA1) and a sodium‐gated potassium channel (KCNT1) cause epilepsy.