Potassium channels are ion channels found in all living things that allow potassium ions to enter and exit cells, creating a charge gradient. There are four types of channels with different functions and structures. They regulate biological functions and are involved in heart rhythm, with potassium channel blocker drugs used to restore normal rhythm.
Potassium channels are a form of ion channel found in nearly all living things. These channels cross cell membranes and provide a means by which potassium ions can enter and exit cells. The movement of potassium in and out of cells creates a potassium gradient that helps set a cell’s action potential and resting membrane potential.
There are four types of potassium ion transport channels. Calcium-activated potassium channels open and close in response to chemical signals from calcium ions. Inward rectifying channels carry a positively charged current into a cell more easily than they carry current out of a cell, allowing for an additional regulatory effect. Tandem pore domain channels are either constantly open or have a high activation rate. These channels allow for rapid movement of potassium. Voltage-gated potassium channels open and close in response to changes in transmembrane voltage.
All types of potassium channels have a characteristic structure. The basic structure of the potassium channel is a tetrameric molecule that forms a class of proteins called integral membrane proteins. The molecule is composed of four identical subunits that form a protein complex with quadruple symmetry. The complex is organized around a central pore through which ions are conducted.
The function of the potassium channel is to transmit potassium ions between cells and extracellular spaces. Most cells maintain a concentration of potassium much higher than the concentration maintained in the extracellular spaces, helping to create a charge gradient across cell membranes. The movement of potassium and other ions such as sodium and calcium through various types of channels is part of an ongoing cellular process that helps regulate many biological functions.
Potassium channels are very ubiquitous in the natural world and are present in nearly all living things. These channels have a wide variety of biological functions, helping regulate action potential in heart muscle, for example, and regulating cellular processes that control the secretion of hormones such as insulin. In neurons, the movement of potassium ions through channels helps set up the action potential, the electrochemical energy wave that allows cells to transmit neurological signals.
Because potassium ion channels are heavily involved in regulating heart rhythm, potassium channel blocker drugs are commonly prescribed for many types of cardiac arrhythmia. When the heart rhythm is abnormal, potassium channel blocking drugs can restore a normal rhythm by increasing the duration of action potentials. These drugs can be used as vasodilators in addition to their more common use as antiarrhythmic drugs.
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