Cation channel superfamily

Last updated
Ion channel (eukaryotic)
2r9r opm.png
Potassium channel Kv1.2 (with beta2 auxiliary subunits), structure in a membrane-like environment. Calculated hydrocarbon boundaries of the lipid bilayer are indicated by red and blue dots.
Identifiers
SymbolIon_trans
Pfam PF00520
InterPro IPR005821
SCOP2 1bl8 / SCOPe / SUPFAM
TCDB 1.A.1
OPM superfamily 8
OPM protein 2a79
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary
PDB 1qg9 A:157-176 2a79 B:225-409 1ho7 A:378-397 1ho2 A:378-397 1ujl A:570-611
Ion channel (bacterial)
1r3j.png
Potassium channel KcsA. Calculated hydrocarbon boundaries of the lipid bilayer are indicated by red and blue dots.
Identifiers
SymbolIon_trans_2
Pfam PF07885
InterPro IPR013099
SCOP2 1bl8 / SCOPe / SUPFAM
OPM protein 1r3j
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary
PDB 1lnq E:25-100 2a0l B:169-250 1orq C:169-250

1k4c C:34-116 1r3i C:34-116 2boc C:34-116 1j95 C:34-116 1r3l C:34-116 1jvm B:34-116 1bl8 C:34-116 2a9h D:34-116 1k4d C:34-116 1r3j C:34-116 1r3k C:34-116 2bob C:34-116

Contents

1p7b B:77-151

The transmembrane cation channel superfamily was defined in InterPro and Pfam as the family of tetrameric ion channels. These include the sodium, potassium, [1] calcium, ryanodine receptor, HCN, CNG, CatSper, and TRP channels. This large group of ion channels apparently includes families 1.A.1 , 1.A.2 , 1.A.3 , and 1.A.4 of the TCDB transporter classification.

They are described as minimally having two transmembrane helices flanking a loop which determines the ion selectivity of the channel pore. Many eukaryotic channels have four additional transmembrane helices (TM) (Pfam PF00520), related to or vestigial of voltage gating. The proteins with only two transmembrane helices (Pfam PF07885) are most commonly found in bacteria. This also includes the 2-TM inward-rectifier potassium channels (Pfam PF01007) found primarily in eukaryotes. There are commonly additional regulatory domains which serve to regulate ion conduction and channel gating. The pores may also be homotetramers or heterotetramers; where heterotetramers may be encoded as distinct genes or as multiple pore domains within a single polypeptide. The HVCN1 and Putative tyrosine-protein phosphatase proteins do not contain an expected ion conduction pore domain, but rather have homology only to the voltage sensor domain of voltage gated ion channels.

Human channels with 6 TM helices

Cation

Transient receptor potential

Canonical
Melastatin
Vanilloid
Mucolipin
Ankyrin
TRPP

Calcium

Voltage-dependent

Sperm

Ryanodine receptor

Potassium

Voltage-gated potassium

Delayed rectifier
A-type potassium
  • Kvα1.x - Shaker-related: Kv1.4 (KCNA4)
  • Kvα3.x - Shaw-related: Kv3.3 (KCNC3), Kv3.4 (KCNC4)
  • Kvα4.x - Shal-related: Kv4.1 (KCND1), Kv4.2 (KCND2), Kv4.3 (KCND3)
Outward-rectifying
Inwardly-rectifying
Slowly activating
Modifier/silencer

Calcium-activated

BK
SK
  • KCa2.x: KCa2.1 (KCNN1) - SK1, KCa2.2 (KCNN2) - SK2, KCa2.3 (KCNN3) - SK3
  • KCa3.x: KCa3.1 (KCNN4) - SK4
  • KCa4.x: KCa4.1 (KCNT1) - SLACK, KCa4.2 (KCNT2) - SLICK
IK
Other subfamilies

Inward-rectifier potassium

Sodium

Cyclic nucleotide-gated

Proton

Human channels with 2 TM helices in each subunit

Potassium

Tandem pore domain potassium channel

Non-human channels

Two-pore

Pore-only potassium

Ligand-gated potassium

Voltage-gated potassium

Prokaryotic KCa

Voltage and cyclic nucleotide gated potassium

Sodium

Non-selective

Prokaryotic inward-rectifier potassium

Engineered

Related Research Articles

<span class="mw-page-title-main">Ion channel</span> Pore-forming membrane protein

Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane, controlling the flow of ions across secretory and epithelial cells, and regulating cell volume. Ion channels are present in the membranes of all cells. Ion channels are one of the two classes of ionophoric proteins, the other being ion transporters.

<span class="mw-page-title-main">Potassium channel</span> Ion channel that selectively passes K+

Potassium channels are the most widely distributed type of ion channel found in virtually all organisms. They form potassium-selective pores that span cell membranes. Potassium channels are found in most cell types and control a wide variety of cell functions.

<span class="mw-page-title-main">Repolarization</span> Change in membrane potential

In neuroscience, repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value. The repolarization phase usually returns the membrane potential back to the resting membrane potential. The efflux of potassium (K+) ions results in the falling phase of an action potential. The ions pass through the selectivity filter of the K+ channel pore.

<span class="mw-page-title-main">Voltage-gated ion channel</span> Type of ion channel transmembrane protein

Voltage-gated ion channels are a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, regulating their opening and closing. Cell membranes are generally impermeable to ions, thus they must diffuse through the membrane through transmembrane protein channels. They have a crucial role in excitable cells such as neuronal and muscle tissues, allowing a rapid and co-ordinated depolarization in response to triggering voltage change. Found along the axon and at the synapse, voltage-gated ion channels directionally propagate electrical signals. Voltage-gated ion-channels are usually ion-specific, and channels specific to sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl−) ions have been identified. The opening and closing of the channels are triggered by changing ion concentration, and hence charge gradient, between the sides of the cell membrane.

The shaker (Sh) gene, when mutated, causes a variety of atypical behaviors in the fruit fly, Drosophila melanogaster. Under ether anesthesia, the fly’s legs will shake ; even when the fly is unanaesthetized, it will exhibit aberrant movements. Sh-mutant flies have a shorter lifespan than regular flies; in their larvae, the repetitive firing of action potentials as well as prolonged exposure to neurotransmitters at neuromuscular junctions occurs.

<span class="mw-page-title-main">Kv1.1</span>

Potassium voltage-gated channel subfamily A member 1 also known as Kv1.1 is a shaker related voltage-gated potassium channel that in humans is encoded by the KCNA1 gene. Isaacs syndrome is a result of an autoimmune reaction against the Kv1.1 ion channel.

Calcium-activated potassium channels are potassium channels gated by calcium, or that are structurally or phylogenetically related to calcium gated channels. They were first discovered in 1958 by Gardos who saw that calcium levels inside of a cell could affect the permeability of potassium through that cell membrane. Then in 1970, Meech was the first to observe that intracellular calcium could trigger potassium currents. In humans they are divided into three subtypes: large conductance or BK channels, which have very high conductance which range from 100 to 300 pS, intermediate conductance or IK channels, with intermediate conductance ranging from 25 to 100 pS, and small conductance or SK channels with small conductances from 2-25 pS.

<span class="mw-page-title-main">Voltage-gated potassium channel</span> Class of transport proteins

Voltage-gated potassium channels (VGKCs) are transmembrane channels specific for potassium and sensitive to voltage changes in the cell's membrane potential. During action potentials, they play a crucial role in returning the depolarized cell to a resting state.

<span class="mw-page-title-main">KCNE1</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel subfamily E member 1 is a protein that in humans is encoded by the KCNE1 gene.

<span class="mw-page-title-main">Potassium channel tetramerisation domain</span>

K+ channel tetramerisation domain is the N-terminal, cytoplasmic tetramerisation domain (T1) of voltage-gated K+ channels. It defines molecular determinants for subfamily-specific assembly of alpha-subunits into functional tetrameric channels. It is distantly related to the BTB/POZ domain Pfam PF00651.

<span class="mw-page-title-main">Calcium-activated potassium channel subunit alpha-1</span> Voltage-gated potassium channel protein

Calcium-activated potassium channel subunit alpha-1 also known as large conductance calcium-activated potassium channel, subfamily M, alpha member 1 (KCa1.1), or BK channel alpha subunit, is a voltage gated potassium channel encoded by the KCNMA1 gene and characterized by their large conductance of potassium ions (K+) through cell membranes.

<span class="mw-page-title-main">KCND2</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel subfamily D member 2 is a protein that in humans is encoded by the KCND2 gene. It contributes to the cardiac transient outward potassium current (Ito1), the main contributing current to the repolarizing phase 1 of the cardiac action potential.

<span class="mw-page-title-main">KCNA4</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel subfamily A member 4 also known as Kv1.4 is a protein that in humans is encoded by the KCNA4 gene. It contributes to the cardiac transient outward potassium current (Ito1), the main contributing current to the repolarizing phase 1 of the cardiac action potential.

<span class="mw-page-title-main">KCNA3</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel, shaker-related subfamily, member 3, also known as KCNA3 or Kv1.3, is a protein that in humans is encoded by the KCNA3 gene.

<span class="mw-page-title-main">KCNE4</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel subfamily E member 4, originally named MinK-related peptide 3 or MiRP3 when it was discovered, is a protein that in humans is encoded by the KCNE4 gene.

<span class="mw-page-title-main">KCNC4</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel, Shaw-related subfamily, member 4 (KCNC4), also known as Kv3.4, is a human gene.

<span class="mw-page-title-main">KCNC1</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel subfamily C member 1 is a protein that in humans is encoded by the KCNC1 gene.

<span class="mw-page-title-main">KCNG1</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel subfamily G member 1 is a protein that in humans is encoded by the KCNG1 gene.

<span class="mw-page-title-main">KCNC3</span> Protein-coding gene in the species Homo sapiens

Potassium voltage-gated channel, Shaw-related subfamily, member 3 also known as KCNC3 or Kv3.3 is a protein that in humans is encoded by the KCNC3.

<span class="mw-page-title-main">Lipid-gated ion channels</span> Type of ion channel transmembrane protein

Lipid-gated ion channels are a class of ion channels whose conductance of ions through the membrane depends directly on lipids. Classically the lipids are membrane resident anionic signaling lipids that bind to the transmembrane domain on the inner leaflet of the plasma membrane with properties of a classic ligand. Other classes of lipid-gated channels include the mechanosensitive ion channels that respond to lipid tension, thickness, and hydrophobic mismatch. A lipid ligand differs from a lipid cofactor in that a ligand derives its function by dissociating from the channel while a cofactor typically derives its function by remaining bound.

References

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