Classification by gating Ion channel

1 classification gating

1.1 voltage-gated
1.2 ligand-gated
1.3 other gating

classification gating

ion channels may classified gating, i.e. opens , closes channels. voltage-gated ion channels open or close depending on voltage gradient across plasma membrane, while ligand-gated ion channels open or close depending on binding of ligands channel.

voltage-gated

voltage-gated ion channels open , close in response membrane potential.

voltage-gated sodium channels: family contains @ least 9 members , largely responsible action potential creation , propagation. pore-forming α subunits large (up 4,000 amino acids) , consist of 4 homologous repeat domains (i-iv) each comprising 6 transmembrane segments (s1-s6) total of 24 transmembrane segments. members of family coassemble auxiliary β subunits, each spanning membrane once. both α , β subunits extensively glycosylated.
voltage-gated calcium channels: family contains 10 members, though these members known coassemble α2δ, β, , γ subunits. these channels play important role in both linking muscle excitation contraction neuronal excitation transmitter release. α subunits have overall structural resemblance of sodium channels , equally large.

cation channels of sperm: small family of channels, referred catsper channels, related two-pore channels , distantly related trp channels.


voltage-gated potassium channels (kv): family contains 40 members, further divided 12 subfamilies. these channels known role in repolarizing cell membrane following action potentials. α subunits have 6 transmembrane segments, homologous single domain of sodium channels. correspondingly, assemble tetramers produce functioning channel.
some transient receptor potential channels: group of channels, referred trp channels, named after role in drosophila phototransduction. family, containing @ least 28 members, incredibly diverse in method of activation. trp channels seem constitutively open, while others gated voltage, intracellular ca, ph, redox state, osmolarity, , mechanical stretch. these channels vary according ion(s) pass, being selective ca while others less selective, acting cation channels. family subdivided 6 subfamilies based on homology: classical (trpc), vanilloid receptors (trpv), melastatin (trpm), polycystins (trpp), mucolipins (trpml), , ankyrin transmembrane protein 1 (trpa).
hyperpolarization-activated cyclic nucleotide-gated channels: opening of these channels due hyperpolarization rather depolarization required other cyclic nucleotide-gated channels. these channels sensitive cyclic nucleotides camp , cgmp, alter voltage sensitivity of channel’s opening. these channels permeable monovalent cations k , na. there 4 members of family, of form tetramers of six-transmembrane α subunits. these channels open under hyperpolarizing conditions, function pacemaking channels in heart, particularly sa node.
voltage-gated proton channels: voltage-gated proton channels open depolarization, in ph-sensitive manner. result these channels open when electrochemical gradient outward, such opening allow protons leave cells. function appears acid extrusion cells. important function occurs in phagocytes (e.g. eosinophils, neutrophils, macrophages) during respiratory burst. when bacteria or other microbes engulfed phagocytes, enzyme nadph oxidase assembles in membrane , begins produce reactive oxygen species (ros) kill bacteria. nadph oxidase electrogenic, moving electrons across membrane, , proton channels open allow proton flux balance electron movement electrically.

ligand-gated

also known ionotropic receptors, group of channels open in response specific ligand molecules binding extracellular domain of receptor protein. ligand binding causes conformational change in structure of channel protein leads opening of channel gate , subsequent ion flux across plasma membrane. examples of such channels include cation-permeable nicotinic acetylcholine receptor, ionotropic glutamate-gated receptors, acid sensing ion channels (asics), atp-gated p2x receptors, , anion-permeable γ-aminobutyric acid-gated gabaa receptor.

ion channels activated second messengers may categorized in group, although ligands , second messengers otherwise distinguished each other.

other gating

gating includes activation , inactivation second messengers inside of cell membrane – rather outside cell, in case ligands.

some potassium channels:

inward-rectifier potassium channels: these channels allow potassium ions flow cell in inwardly rectifying manner: potassium flows more efficiently out of cell. family composed of 15 official , 1 unofficial members , further subdivided 7 subfamilies based on homology. these channels affected intracellular atp, pip2, , g-protein βγ subunits. involved in important physiological processes such pacemaker activity in heart, insulin release, , potassium uptake in glial cells. contain 2 transmembrane segments, corresponding core pore-forming segments of kv , kca channels. α subunits form tetramers.
calcium-activated potassium channels: family of channels activated intracellular ca , contains 8 members.
two-pore-domain potassium channels: family of 15 members form known leak channels, , display goldman-hodgkin-katz (open) rectification.


light-gated channels channelrhodopsin directly opened photons.
mechanosensitive ion channels open under influence of stretch, pressure, shear, , displacement.
cyclic nucleotide-gated channels: superfamily of channels contains 2 families: cyclic nucleotide-gated (cng) channels , hyperpolarization-activated, cyclic nucleotide-gated (hcn) channels. should noted grouping functional rather evolutionary.

cyclic nucleotide-gated channels: family of channels characterized activation either intracellular camp or cgmp. these channels permeable monovalent cations such k , na. permeable ca, though acts close them. there 6 members of family, divided 2 subfamilies.
hyperpolarization-activated cyclic nucleotide-gated channels


temperature-gated channels: members of transient receptor potential ion channel superfamily, such trpv1 or trpm8, opened either hot or cold temperatures.




^ hanukoglu (february 2017). asic , enac type sodium channels: conformational states , structures of ion selectivity filters . febs journal. 284 (4): 525–545. doi:10.1111/febs.13840. pmid 27580245.