Potassium Channels

Potassium channels are crucial regulators of membrane excitability. They control the frequency and shape of action potentials, regulate secretion of hormones and neurotransmitters and establish cell plasma membrane potential. This large family can be regulated by voltage, Ca2+, neurotransmitters and the signaling pathways that they stimulate. Structurally, potassium channels exist as tetramers and the pore forming entity is the α-subunit. There are more than 70 different genes encoding the K+ α-subunit in the human genome.

Ion Channel Data

The Proposed Structure of Voltage-Gated Potassium Channels

The figure below shows the proposed structure of voltage-gated potassium channels.

A single α subunit

A. A single α subunit showing the K+ ion selectivity signature motif 'T/SxxTxGYG' within the pore loop.

The general assembly of the K<sup>+</sup> channel

B. The general assembly of the K+ channel; composed of four, P loop-containing α-subunits arranged in a tetrameric fashion.

The table below summarizes the key characteristics of some potassium channels.

Properties of Potassium Channels

Type Inward Rectifier ATP-Sensitive Voltage-Sensitive Ca2+-Activated
Subtype - - A-type Delayed rectifier Large conductance (maxi-K, BK) Small conductance (SK)
Effect of Ca2+ Insensitive Insensitive Insensitive Insensitive Variable High sensitivity
Effect of Voltage Strong, inward rectification Weak, inward rectification Sensitive Sensitive Sensitive Insensitive
Effect of ATP Insensitive Inhibits channel opening Insensitive Insensitive Insensitive Insensitive
Conductance (pS) 5-30 5-90 < 1-20 < 1-20 100-250 6-14


Robertson et al (1997) The real life of voltage-gated K+ channels: more than model behaviour. TiPS 18 474. Mathie et al (1998) Voltage-activated potassium channels in mammalian neurons and their block by novel pharmacological agents. Gen.Pharmacol. 30 13. Vergara et al (1998) Calcium-activated potassium channels. Curr.Opin.Neurobiol. 8 321.