Domain

Voltage-dependent calcium channel, alpha-1 subunit, IQ domain (IPR014873)

Short name: VDCC_a1su_IQ

Domain relationships

None.

Description

Ca2+ ions are unique in that they not only carry charge but they are also the most widely used of diffusible second messengers. Voltage-dependent Ca2+ channels (VDCC) are a family of molecules that allow cells to couple electrical activity to intracellular Ca2+ signalling. The opening and closing of these channels by depolarizing stimuli, such as action potentials, allows Ca2+ ions to enter neurons down a steep electrochemical gradient, producing transient intracellular Ca2+ signals. Many of the processes that occur in neurons, including transmitter release, gene transcription and metabolism are controlled by Ca2+ influx occurring simultaneously at different cellular locales. The pore is formed by the alpha-1 subunit which incorporates the conduction pore, the voltage sensor and gating apparatus, and the known sites of channel regulation by second messengers, drugs, and toxins [PMID: 14657414]. The activity of this pore is modulated by 4 tightly-coupled subunits: an intracellular beta subunit; a transmembrane gamma subunit; and a disulphide-linked complex of alpha-2 and delta subunits, which are proteolytically cleaved from the same gene product. Properties of the protein including gating voltage-dependence, G protein modulation and kinase susceptibility can be influenced by these subunits.

Voltage-gated calcium channels are classified as T, L, N, P, Q and R, and are distinguished by their sensitivity to pharmacological blocks, single-channel conductance kinetics, and voltage-dependence. On the basis of their voltage activation properties, the voltage-gated calcium classes can be further divided into two broad groups: the low (T-type) and high (L, N, P, Q and R-type) threshold-activated channels.

The voltage-gated calcium channel alpha 1 subunit contains an IQ domain, named for its isoleucine-glutamine (IQ) motif, which interacts with hydrophobic pockets of Ca2+/calmodulin [PMID: 16299511]. The interaction regulates two self-regulatory calcium dependent feedback mechanisms, calcium dependent inactivation (CDI), and calcium-dependent facilitation (CDF).

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
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