intermediate conductance calcium-activated potassium channel activity

Definition

Target type: molecularfunction

Enables the transmembrane transfer of potassium by a channel with a unit conductance of 20 to 85 picoSiemens that opens in response to stimulus by internal calcium ions. Intermediate conductance calcium-activated potassium channels are more sensitive to calcium than are large conductance calcium-activated potassium channels. Transport by a channel involves catalysis of facilitated diffusion of a solute (by an energy-independent process) involving passage through a transmembrane aqueous pore or channel, without evidence for a carrier-mediated mechanism. [GOC:mtg_transport, OMIM:602754]

Intermediate conductance calcium-activated potassium (IKCa) channels are membrane proteins that play a crucial role in regulating cellular excitability and calcium signaling. Their molecular function involves the selective passage of potassium ions (K+) across the cell membrane in response to changes in intracellular calcium concentration. This process is essential for maintaining normal physiological functions in various tissues, including the nervous system, smooth muscle, and endocrine glands.

IKCa channels are composed of four subunits, each containing six transmembrane domains. These subunits assemble into a tetrameric structure, forming a pore through which K+ ions can flow. The channel's opening and closing is regulated by the binding of calcium ions (Ca2+) to specific sites within the channel protein. Increased intracellular Ca2+ concentration, often triggered by various stimuli such as neurotransmitters, hormones, or depolarization, leads to channel activation and K+ efflux.

The molecular mechanism underlying this Ca2+-dependent activation involves a complex interplay between conformational changes within the channel protein and the interaction with Ca2+ ions. The binding of Ca2+ to specific domains within the channel protein induces a change in the channel's conformation, leading to the opening of the pore. This opening allows K+ ions to flow down their electrochemical gradient, out of the cell. The resulting K+ efflux contributes to membrane repolarization and the termination of action potentials in excitable cells. In non-excitable cells, IKCa channels regulate various cellular processes, including cell volume regulation, smooth muscle contraction, and hormone secretion.

The specific characteristics of IKCa channels, such as their sensitivity to calcium and their conductance, vary depending on the specific channel subtype and the tissue in which they are expressed. These variations contribute to the diversity of functions that IKCa channels play in different cell types and tissues.

In summary, the molecular function of IKCa channels involves the selective passage of K+ ions across the cell membrane in response to changes in intracellular Ca2+ concentration. This process is essential for regulating cellular excitability, calcium signaling, and various other cellular processes in different tissues.'
"

Proteins (1)

Compounds (4)