View source for Ion channel

{{dablink|Another, unrelated ion channeling process is part of [[ion implantation]].}}
:''Not to be confused with:'' [[Ion Television]].
[[Image:Ion channel.png|thumb|350px|Schematic diagram of an ion channel. '''1''' - channel [[protein domain|domain]]s (typically four per channel), '''2''' - outer vestibule, '''3''' - [[Potassium_channel#Selectivity_filter|selectivity filter]], '''4''' - diameter of selectivity filter, '''5''' - [[phosphorylation]] site, '''6''' - [[cell membrane]].]]
'''Ion channels''' are pore-forming [[protein]]s that help establish and control the small [[voltage]] [[gradient]] across the [[plasma membrane]] of all living [[cell (biology)|cell]]s (see [[cell potential]]) by allowing the flow of [[ion]]s down their [[electrochemical gradient]].<ref name="isbn0-87893-321-2">{{cite book | author = Hille, Bertil | authorlink = | editor = | others = | title = Ion channels of excitable membranes | edition = third | language = | publisher = Sinauer Associates | location = Sunderland, Mass | year = 2001 | origyear = | pages = | quote = | isbn = 0-87893-321-2 | oclc = | doi = | url = | accessdate = }}</ref> They are present in the [[cell membrane|membrane]]s that surround all [[cell (biology)|biological cell]]s. The study of ion channels involves many scientific techniques such as [[voltage clamp]] [[electrophysiology]] (in particular [[patch clamp]]), [[immunohistochemistry]], and [[RT-PCR]].

== Basic features ==

Ion channels regulate the flow of ions across the membrane in all cells. Ion channels are [[integral membrane protein]]s; or, more typically, an assembly of several proteins.  Such "multi-[[protein subunit|subunit]]" assemblies usually involve a circular arrangement of identical or [[homology (biology)|homologous]] proteins closely packed around a water-filled pore through the plane of the membrane or [[lipid bilayer]].<ref name="isbn0-87893-741-2">{{cite book | author = Purves,| authorlink = | editor = Dale Purves, George J. Augustine, David Fitzpatrick, Lawrence. C. Katz, Anthony-Samuel LaMantia, James O. McNamara, S. Mark Williams, editors | others = | title = Neuroscience | edition = 2nd | language = | publisher = Sinauer Associates Inc. | location = | year = 2001 | origyear = | pages = | chapter = Chapter 4: Channels and Transporters | quote = | isbn = 0-87893-741-2 | oclc = | doi = | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=neurosci.chapter.227 | accessdate = }}</ref><ref name="isbn0-397-51820-X">{{cite book | author =  Hille B, Catterall, WA | authorlink = | editor = George J Siegel, Bernard W Agranoff, R. W Albers, Stephen K Fisher and Michael D Uhler | others = | title = Basic neurochemistry: molecular, cellular, and medical aspects | edition = | language = | publisher = Lippincott-Raven | location = Philadelphia | year = 1999 | origyear = | pages = | chapter = Chapter 6: Electrical Excitability and Ion Channels| quote = | isbn = 0-397-51820-X | oclc = | doi = | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=bnchm.chapter.421 | accessdate = }}</ref> For most [[voltage-gated ion channel]]s, the pore-forming subunit(s) are called the α subunit, while the auxiliary subunits are denoted β, γ, and so on. Some channels permit the passage of ions based solely on their charge of positive (cation) or negative (anion). However, the archetypal channel pore is just one or two atoms wide at its narrowest point and is selective for specific species of ion, such as [[sodium]] or [[potassium]]. These ions move through the channel pore single file nearly as quickly as the ions move through free fluid.  In some ion channels, passage through the pore is governed by a "gate," which may be opened or closed by chemical or electrical signals, temperature, or mechanical force, depending on the variety of channel.

== Biological role ==

Because "voltage-activated" channels underlie the [[nerve impulse]] and because "transmitter-activated" channels mediate conduction across the [[synapse]]s, channels are especially prominent components of the [[nervous system]]. Indeed, most of the offensive and defensive toxins that organisms have evolved for shutting down the nervous systems of predators and prey (e.g., the venoms produced by spiders, scorpions, snakes, fish, bees, sea snails and others) work by modulating ion channel conductance and/or kinetics. In addition, ion channels are key components in a wide variety of biological processes that involve rapid changes in cells, such as [[cardiac muscle|cardiac]], [[skeletal muscle|skeletal]], and [[smooth muscle]] [[Muscle contraction|contraction]], [[epithelium|epithelial]] transport of nutrients and ions, [[T-cell]] activation and [[pancreas|pancreatic]] beta-cell [[insulin]] release. In the search for new drugs, ion channels are a frequent target.<ref name="pmid17395128">{{cite journal | author = Camerino DC, Tricarico D, Desaphy JF | title = Ion channel pharmacology | journal = Neurotherapeutics | volume = 4 | issue = 2 | pages = 184–98 | year = 2007 | month = April | pmid = 17395128 | doi = 10.1016/j.nurt.2007.01.013 | url = | issn = }}</ref><ref name="pmid19153558">{{cite journal | author = Verkman AS, Galietta LJ | title = Chloride channels as drug targets | journal = Nat Rev Drug Discov | volume = 8 | issue = 2 | pages = 153–71 | year = 2009 | month = February | pmid = 19153558 | doi = 10.1038/nrd2780 | url = | issn = }}</ref><ref name="pmid19161833">{{cite journal | author = Camerino DC, Desaphy JF, Tricarico D, Pierno S, Liantonio A | title = Therapeutic approaches to ion channel diseases | journal = Adv. Genet. | volume = 64 | issue = | pages = 81–145 | year = 2008 | pmid = 19161833 | doi = 10.1016/S0065-2660(08)00804-3 | url = | issn = }}</ref>

==Diversity==

There are over 300 types of ion channels in a living cell.<ref name="pmid17541769">{{cite journal | author = Gabashvili IS, Sokolowski BH, Morton CC, Giersch AB | title = Ion channel gene expression in the inner ear | journal = J. Assoc. Res. Otolaryngol. | volume = 8 | issue = 3 | pages = 305–28 | year = 2007 | month = September | pmid = 17541769 | pmc = 2538437 | doi = 10.1007/s10162-007-0082-y | url = | issn = }}</ref> Ion channels may be classified by the nature of their gating, the species of ions passing through those gates, and the number of gates (pores).

Further heterogeneity of ion channels arises when channels with different constitutive [[Protein subunit|subunits]] give rise to a specific kind of current.<ref>{{cite journal |author=Vicini S |title=New perspectives in the functional role of GABA(A) channel heterogeneity |journal=Mol. Neurobiol. |volume=19 |issue=2 |pages=97–110 |year=1999 |month=April |pmid=10371465 |doi=10.1007/BF02743656 |url=}}</ref> Absence or mutation of one or more of the contributing types of channel subunits can result in loss of function and, potentially, underly neurologic diseases.

===By gating===

Ion channels may be classified by gating, i.e. what opens and closes the channels. Voltage-gated ion channels open or close depending on the voltage gradient across the plasma membrane, while ligand-gated ion channels open or close depending on binding of [[Ligand (biochemistry)|ligands]] to the channel.

====Voltage-gated====

{{Main|Voltage-gated ion channel}}
Voltage-gated ion channels open and close in response to [[membrane potential]].

*[[Voltage-gated sodium channel]]s: This family contains at least 9 members and is largely responsible for [[action potential]] creation and propagation. The pore-forming α subunits are very large (up to 4,000 [[amino acid]]s) and consist of four homologous repeat domains (I-IV) each comprising six transmembrane segments (S1-S6) for a total of 24 transmembrane segments. The members of this family also coassemble with auxiliary β subunits, each spanning the membrane once.  Both α and β subunits are extensively [[glycosylation|glycosylated]].

*[[Voltage-gated calcium channel]]s: This family contains 10 members, though these members are known to coassemble with α<sub>2</sub>δ, β, and γ subunits. These channels play an important role in both linking muscle excitation with contraction as well as neuronal excitation with transmitter release. The α subunits have an overall structural resemblance to those of the sodium channels and are equally large.
**[[Cation channels of sperm]]: This small family of channels, normally referred to as Catsper channels, is related to the [[two-pore channels]] and distantly related to [[Transient response potential channel|TRP channels]].

*[[Voltage-gated potassium channel]]s (K<sub>V</sub>): This family contains almost 40 members, which are further divided into 12 subfamilies. These channels are known mainly for their role in repolarizing the cell membrane following [[action potential]]s.  The α subunits have six transmembrane segments, homologous to a single domain of the sodium channels.  Correspondingly, they assemble as [[tetramer protein|tetramer]]s to produce a functioning channel.

*Some [[transient receptor potential channel]]s: This group of channels, normally referred to simply as TRP channels, is named after their role in [[Drosophila]] phototransduction. This family, containing at least 28 members, is incredibly diverse in its method of activation. Some TRP channels seem to be constitutively open, while others are gated by [[Voltage-gated ion channel|voltage]], intracellular Ca<sup>2+</sup>, pH, redox state, osmolarity, and [[Stretch-activated ion channel|mechanical stretch]]. These channels also vary according to the ion(s) they pass, some being selective for Ca<sup>2+</sup> while others are less selective, acting as cation channels. This family is subdivided into 6 subfamilies based on homology: classical ([[TRPC]]), vanilloid receptors ([[TRPV]]), melastatin ([[TRPM]]), polycystins ([[TRPP]]), mucolipins ([[TRPML]]), and ankyrin transmembrane protein 1 ([[TRPA]]).

*Hyperpolarization-activated [[cyclic nucleotide-gated channel]]s: The opening of these channels is due to [[Hyperpolarization (biology)|hyperpolarization]] rather than the depolarization required for other cyclic nucleotide-gated channels. These channels are also sensitive to the cyclic nucleotides [[cAMP]] and [[cGMP]], which alter the voltage sensitivity of the channel’s opening. These channels are permeable to the monovalent cations K<sup>+</sup> and Na<sup>+</sup>. There are 4 members of this family, all of which form tetramers of six-transmembrane α subunits.  As these channels open under hyperpolarizing conditions, they function as [[Cardiac pacemaker|pacemaking]] channels in the heart, particularly the [[SA node]].

*[[Voltage-gated proton channel]]s: Voltage-gated proton channels open with depolarization, but in a strongly pH-sensitive manner. The result is that these channels open only when the electrochemical gradient is outward, such that their opening will only allow protons to leave cells. Their function thus appears to be acid extrusion from cells. Another important function occurs in phagocytes (e.g. [[eosinophils]], [[neutrophils]], [[macrophages]]) during the "respiratory burst."  When bacteria or other microbes are engulfed by phagocytes, the enzyme [[NADPH oxidase]] assembles in the membrane and begins to produce [[reactive oxygen species]] (ROS) that help kill bacteria.  NADPH oxidase is electrogenic, moving electrons across the membrane, and proton channels open to allow proton flux to balance the electron movement electrically.

==== Ligand-gated ====
{{Main|Ligand-gated ion channel}}

Also known as ionotropic [[receptor (biochemistry)|receptors]], this group of channels open in response to specific ligand molecules binding to the extracellular domain of the receptor protein. Ligand binding causes a conformational change in the structure of the channel protein that ultimately leads to the opening of the channel gate and subsequent ion flux across the plasma membrane. Examples of such channels include the cation-permeable [[Acetylcholine receptor|"nicotinic" Acetylcholine receptor]], [[Glutamate receptors|ionotropic glutamate-gated receptors]] and [[P2X Receptors|ATP-gated P2X receptors]], and the anion-permeable γ-aminobutyric acid-gated [[GABA receptor|GABA<sub>A</sub> receptor]].

Ion channels activated by second messengers may also be categorized in this group, although [[Ligand (biochemistry)|ligands]] and second messengers are otherwise distinguished from each other.

==== Other gating ====

Other gating include activation/inactivation by e.g. [[second messenger]]s from the inside of the [[cell membrane]], rather as from outside, as in the case for ligands. Ions may count to such second messengers, and then causes direct activation, rather than indirect, as in the case were the electric potential of ions cause activation/inactivation of voltage-gated ion channels.

*Some potassium channels
**[[Inward-rectifier potassium ion channel|Inward-rectifier potassium channels]]: These channels allow potassium to flow into the cell in an inwardly rectifying manner, i.e., potassium flows effectively into, but not out of, the cell. This family is composed of 15 official and 1 unofficial members and is further subdivided into 7 subfamilies based on homology. These channels are affected by intracellular [[Adenosine triphosphate|ATP]], PIP<sub>2</sub>, and [[G-protein]] βγ subunits. They are involved in important physiological processes such as the pacemaker activity in the heart, insulin release, and potassium uptake in [[glia|glial cells]].  They contain only two transmembrane segments, corresponding to the core pore-forming segments of the K<sub>V</sub> and K<sub>Ca</sub> channels.  Their α subunits form tetramers.
**[[Calcium-activated potassium channel]]s: This family of channels is, for the most part, activated by intracellular Ca<sup>2+</sup> and contains 8 members.
**[[Tandem pore domain potassium channel|Two-pore-domain potassium channels]]: This family of 15 members form what is known as [[leak channel]]s, and they follow [[GHK current equation|Goldman-Hodgkin-Katz]] (open) [[rectifier|rectification]].

*[[Light-gated ion channels|Light-gated channels]] like [[channelrhodopsin]] are directly opened by the action of light.

*[[Mechanosensitive ion channel]]s are opening under the influence of stretch, pressure, shear, displacement.

*[[Cyclic nucleotide-gated channels]]: This superfamily of channels contains two families: the cyclic nucleotide-gated (CNG) channels and the hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels. It should be noted that this grouping is functional rather than evolutionary.
**Cyclic nucleotide-gated channels: This family of channels is characterized by activation due to the binding of intracellular [[cAMP]] or [[cGMP]], with specificity varying by member. These channels are primarily permeable to monovalent cations such as K<sup>+</sup> and Na<sup>+</sup>. They are also permeable to Ca<sup>2+</sup>, though it acts to close them. There are 6 members of this family, which is divided into 2 subfamilies.
**Hyperpolarization-activated [[cyclic nucleotide-gated channels]]

*Temperature Gated Channels: Members of the [[Trp channel|Transient Receptor Potential ion channel]] superfamily, such as [[TRPV1]] or [[TRPM8]] are opened either by hot or cold temperatures.

===By ions===
*[[Chloride channel]]s: This superfamily of poorly-understood channels consists of approximately 13 members.

*[[Potassium channel]]s
**[[Voltage-gated potassium channel]]s
**[[Calcium-activated potassium channel]]s 
**[[Inward-rectifier potassium ion channel|Inward-rectifier potassium channels]]
**[[Two P potassium channel|Two-pore-domain potassium channels]]: This family of 15 members form what is known as [[leak channel]]s, and they follow [[GHK current equation|Goldman-Hodgkin-Katz]] (open) [[rectifier|rectification]]. 

*[[Sodium channels]]
** [[voltage-gated sodium channel]]s
** [[epithelial sodium channel]]s (ENaC)

*[[Calcium channel]]s

*Proton channels
**[[Voltage-gated proton channels]]

*''Non-selective cation channels'': These let many types of cations, mainly Na<sup>+</sup>, K<sup>+</sup> and Ca<sup>2+</sup> through the channel.
**Most [[Transient receptor potential|Transient receptor potential channels]]

=== Other classifications ===

There are other types of ion channel classifications that are based on less normal characteristics, e.g. multiple pores and transient potentials.

Almost all ion channels have one single pore. However, there are also those with two:
*[[Two-pore channel]]s: This small family of 2 members putatively forms cation-selective ion channels.  They are predicted to contain two K<sub>V</sub>-style six-transmembrane domains, suggesting they form a dimer in the membrane. These channels are related to [[Cation channels of sperm|catsper channels]] channels and, more distantly, [[Transient receptor potential|TRP]] channels.

There are channels that are classified by the duration of the response to stimuli:
*[[Transient receptor potential channel]]s: This group of channels, normally referred to simply as TRP channels, is named after their role in [[Drosophila]] phototransduction. This family, containing at least 28 members, is incredibly diverse in its method of activation. Some TRP channels seem to be constitutively open, while others are gated by [[Voltage-gated ion channel|voltage]], intracellular Ca<sup>2+</sup>, pH, redox state, osmolarity, and [[Stretch-activated ion channel|mechanical stretch]]. These channels also vary according to the ion(s) they pass, some being selective for Ca<sup>2+</sup> while others are less selective, acting as cation channels. This family is subdivided into 6 subfamilies based on homology: canonical ([[TRPC]]), vanilloid receptors ([[TRPV]]), melastatin ([[TRPM]]), polycystins ([[TRPP]]), mucolipins ([[TRPML]]), and ankyrin transmembrane protein 1 ([[TRPA]]).

== Detailed structure ==

Channels differ with respect to the ion they let pass (for example, Na<sup>+</sup>, K<sup>+</sup>, Cl<sup>&minus;</sup>), the ways in which they may be regulated, the number of subunits of which they are composed and other aspects of structure. Channels belonging to the largest class, which includes the voltage-gated channels that underlie the nerve impulse, consists of four subunits with six [[transmembrane helix|transmembrane helices]] each. On activation, these helices move about and open the pore. Two of these six helices are separated by a loop that lines the pore and is the primary determinant of ion selectivity and conductance in this channel class and some others. The existence and mechanism for ion selectivity was first postulated in the 1960s by [[Clay Armstrong]].<ref name="pmid4644327">{{cite journal | author = Bezanilla F, Armstrong CM | title = Negative conductance caused by entry of sodium and cesium ions into the potassium channels of squid axons | journal = J. Gen. Physiol. | volume = 60 | issue = 5 | pages = 588–608 | year = 1972 | month = November | pmid = 4644327 | pmc = 2226091 | doi = 10.1085/jgp.60.5.588| url = | issn = }}</ref> He suggested that the pore lining could efficiently replace the water molecules that normally shield potassium ions, but that sodium ions were too small to allow such shielding, and therefore could not pass through. This mechanism was finally confirmed when the structure of the channel was elucidated. The channel subunits of one such other class, for example, consist of just this "P" loop and two transmembrane helices. The determination of their molecular structure by [[Roderick MacKinnon]] using [[crystallography|X-ray crystallography]] won a share of the 2003 [[Nobel Prize in Chemistry]].

Because of their small size and the difficulty of crystallizing integral membrane proteins for X-ray analysis, it is only very recently that scientists have been able to directly examine what channels "look like." Particularly in cases where the crystallography required removing channels from their membranes with detergent, many researchers regard images that have been obtained as tentative. An example is the long-awaited crystal structure of a voltage-gated potassium channel, which was reported in May 2003.<ref name="pmid12721618">{{cite journal | author = Jiang Y, Lee A, Chen J, Ruta V, Cadene M, Chait BT, MacKinnon R | title = X-ray structure of a voltage-dependent K+ channel | journal = Nature | volume = 423 | issue = 6935 | pages = 33–41 | year = 2003 | month = May | pmid = 12721618 | doi = 10.1038/nature01580 | url = | issn = }}</ref><ref>The detailed 3D structure of the magnesium channel from bacteria can be seen [http://www.nature.com/nature/journal/v440/n7085/fig_tab/nature04642_ft.html here].</ref> One inevitable ambiguity about these structures relates to the strong evidence that channels change conformation as they operate (they open and close, for example), such that the structure in the crystal could represent any one of these operational states. Most of what researchers have deduced about channel operation so far they have established through [[electrophysiology]], [[biochemistry]], [[gene]] sequence comparison and [[mutagenesis]].

==Diseases of ion channels==

There are a number of chemicals and genetic disorders which disrupt normal functioning of ion channels and have disastrous consequences for the organism. Genetic disorders of ion channels and their modifiers are known as [[Channelopathy|Channelopathies]]. See [[:Category:Channelopathy]] for a full list.

'''Chemicals'''
* [[Tetrodotoxin]] (TTX), used by [[puffer fish]] and some types of [[newts]] for defense.  It blocks sodium channels.
* [[Saxitoxin]], is produced by a [[dinoflagellate]] also known as "[[red tide]]".  It blocks voltage dependent sodium channels.
* [[Conotoxin]], is used by [[cone snails]] to hunt prey.  
* [[Lidocaine]] and [[Novocaine]] belong to a class of [[local anesthetics]] which block sodium ion channels.
* [[Dendrotoxin]] is produced by [[mamba]] [[snakes]], and blocks potassium channels.
* [[Iberiotoxin]] is produced by the ''Buthus tamulus'' and blocks potassium channels.
* [[Heteropodatoxin]] is produced by ''Heteropoda venatoria'' and blocks potassium channels.
'''Genetic'''
* [[Shaker gene]] mutations cause a defect in the voltage gated ion channels, slowing down the repolarization of the cell.
* [[Equine hyperkalaemic periodic paralysis]] as well as [[Human hyperkalaemic periodic paralysis]] (HyperPP) are caused by a defect in voltage dependent sodium channels.
* [[Paramyotonia congenita]] (PC) and [[potassium aggravated myotonias]] (PAM)
* [[Generalized epilepsy with febrile seizures plus]] (GEFS+)
* [[Episodic Ataxia]] (EA), characterized by sporadic bouts of severe discoordination with or without myokymia, and can be provoked by stress, startle, or heavy exertion such as exercise.
* [[Familial hemiplegic migraine]] (FHM)
* [[Spinocerebellar ataxia type 13]]
* [[Long QT syndrome]] is a [[Ventricle (heart)|ventricular]] [[arrhythmia]] [[syndrome]] caused by [[mutation]]s in one or more of presently ten different [[gene]]s, most of which are [[potassium channel]]s and all of which affect cardiac [[repolarization]].
* [[Brugada syndrome]] is another ventricular arrhythmia caused by [[voltage-gated sodium channel]] gene mutations.
* [[Cystic fibrosis]] is caused by mutations in the CFTR gene, which is a chloride channel.
* [[Mucolipidosis type IV]] is caused by mutations in the gene encoding the [[TRPML1]] channel

== History ==
The fundamental properties of currents mediated by ion channels were analyzed by the British [[biophysics|biophysicist]]s [[Alan Hodgkin]] and [[Andrew Huxley]] as part of their [[Nobel Prize in Physiology or Medicine|Nobel Prize]]-winning research on the [[action potential]], published in 1952. They built on the work of other physiologists, such as Cole and Baker's research into voltage-gated membrane pores from 1941<ref>
{{cite journal
 | author = Ronald Pethig and Douglas B Kell
 | year = 1987
 | title = The passive electrical properties of biological systems:  their significance in physiology, biophysics and biotechnology.
 | journal = Phys. Med. Biol.
 | volume = 32
 | issue = 8
 | pages = 933–970
 | pmid = 3306721 
 | url = http://dbkgroup.org/Papers/pethig_kell_pmb87.pdf
 | laysummary = An expansive review of bioelectrical characteristics from 1987.
 | quote = ... the observation of an inductance (negative capacitance) by Cole and Baker (1941) during measurements of the AC electrical properties of squid axons led directly to the concept of voltage-gated membrane pores, as embodied in the celebrated Hodgkin-Huxley (1952) treatment (Cole 1972, Jack er a1 1975), as the crucial mechanism of neurotransmission.
 | doi = 10.1088/0031-9155/32/8/001
 }}
</ref><ref>
{{cite journal
 | quotes = 
 | author = KENNETH S. COLE AND RICHARD F. BAKER
 | year = 1941
 | month = February
 | title = LONGITUDINAL IMPEDANCE OF THE SQUID GIANT AXON.
 | journal = The Journal of General Physiology
 | volume = 24
 | issue = 6
 | pages = 771
 | publisher = The Rockefeller University Press
 | pmid = 19873252
 | url = http://jgp.rupress.org/cgi/reprint/24/6/771
 | laysummary = Describes what happens when you stick a [[giant squid axon]] with electrodes and pass through an alternating current, and then notice that sometimes the voltage rises with time, and sometimes it decreases. 
 | laysource = 
 | laydate = 
 | quote = The inductive reactance is a property of the axon and requires that it
contain an inductive structure. The variation of the impedance with interpolar
distance indicates that the inductance is in the membrane
 | doi = 10.1085/jgp.24.6.771
 | pmc = 2238007
 }}
</ref>. The existence of ion channels was confirmed in the 1970s by [[Bernard Katz]] and [[Ricardo Miledi]] using noise analysis. It was then shown more directly with an [[electrophysiology|electrical recording technique]] known as the "[[patch clamp]]", which led to a Nobel Prize to [[Erwin Neher]] and [[Bert Sakmann]], the technique's inventors. Hundreds if not thousands of researchers continue to pursue a more detailed understanding of how these proteins work. In recent years the development of [[Electrophysiology#Planar patch clamp|automated patch clamp devices]] helped to increase significantly the throughput in ion channel screening.

The Nobel Prize in Chemistry for 2003 was awarded to two American scientists: [[Roderick MacKinnon]] for his studies on the physico-chemical properties of ion channel structure and function, including [[x-ray crystallography|x-ray crystallographic]] [[protein structure|structure]] studies, and [[Peter Agre]] for his similar work on [[aquaporin]]s.<ref>{{cite press release |url=http://nobelprize.org/nobel_prizes/chemistry/laureates/2003/press.html |title=The Nobel Prize in Chemistry 2003 |publisher=The Royal Swedish Academy of Science |date=2003-10-08 |accessdate=2010-01-18}}</ref>

== The ion channel in fine art ==
[[Image:Birth of an Idea.jpg|thumb|right|''Birth of an Idea'' (2007) by [[Julian Voss-Andreae]]. The sculpture was commissioned by [[Roderick MacKinnon]] based on the molecule's atomic coordinates that were determined by MacKinnon's group in 2001.]]

Roderick MacKinnon commissioned ''Birth of an Idea'', a 5' (1.50 m) tall sculpture based on the KcsA potassium channel.<ref>{{cite journal | first = Philip | last = Ball | year = 2008 | month = March | title = The crucible: Art inspired by science should be more than just a pretty picture | journal = Chemistry World | volume = 5 | pages = 42–43 | url = http://www.rsc.org/chemistryworld/Issues/2008/March/ColumnThecrucible.asp | accessdate=2009-01-12 | issue = 3}}</ref> The artwork contains a wire object representing the pore liner with a blown glass object representing the main cavity of the channel structure.

==See also==
{{multicol}}
* [[Action potential]]
* [[Active transport]]
* [[Channelome]]
* [[Channelomics]]
* [[Channelopathy]]
* [[Neurotoxin]]
* [[Magnesium transport]]
<!--{{multicol-break}}-->
* [[Passive transport]]
* [[Transmembrane receptor]]
* [[Wikipedia:MeSH D12.776#MeSH D12.776.543.550.425|MeSH entry for Ion channels]]
* [[Ki Database|K<sub>i</sub> Database]]
* [[Ion channel family]] as defined in [[Pfam]] and [[InterPro]]
{{multicol-end}}
{{clear}}

==References==
{{Reflist|2}}

==Further reading==
* [http://www.vega.org.uk/video/programme/121 An Interview with Roderick MacKinnon] Freeview video by the Vega Science Trust.
* {{cite journal | author = Doyle DA, Morais Cabral J, Pfuetzner RA, Kuo A, Gulbis JM, Cohen SL, Chait BT, MacKinnon R | title = The structure of the potassium channel: molecular basis of K+ conduction and selectivity | journal = Science | volume = 280 | issue = 5360 | pages = 69–77 | year = 1998 | month = April | pmid = 9525859 | doi = 10.1126/science.280.5360.69 | url = http://www.cellbio.wustl.edu/faculty/huettner/69.pdf | issn = }}
* {{cite journal | author = Bezanilla F | title = The voltage sensor in voltage-dependent ion channels | journal = Physiol. Rev. | volume = 80 | issue = 2 | pages = 555–92 | year = 2000 | month = April | pmid = 10747201 | doi = | url = http://physrev.physiology.org/cgi/content/abstract/80/2/555 | issn = }}
*{{cite journal  | author=Singh H |title=Two decades with dimorphic Chloride Intracellular Channels (CLICs). |journal=Febs letters.|volume= 584|issue=  10|pages=  2112–21|year= 2010 |pmid= 20226783 |doi=10.1016/j.febslet.2010.03.013 }}
* {{cite news | author=Kathy Liszewski | title=Opening the Gates on Ion Channel Drugs
 | url=http://www.genengnews.com/articles/chitem.aspx?aid=2159 | work=Genetic Engineering & Biotechnology News
 | publisher=[[Mary Ann Liebert, Inc.]] | pages=18, 20 | date=2007-06-15 | accessdate=2008-07-06
 | quote=Conditions targeted include diabetes, cystic fibrosis, hypertension, pain and cancer }}

==External links==
{{wikiversity|Poisson–Boltzmann profile for an ion channel}}
*{{cite web | url = http://www.iuphar-db.org/DATABASE/ReceptorFamiliesForward?type=IC| title = Voltage-Gated Ion Channels | accessdate = | author = | authorlink = | coauthors = | date = | format = | work = IUPHAR Database of Receptors and Ion Channels | publisher = International Union of Basic and Clinical Pharmacology | pages = | language = | archiveurl = | archivedate = | quote = }}
* {{cite web | url = http://www.trpchannel.org | title = TRIP Database | accessdate = | author = | authorlink = | coauthors = | date = | format = | work = a manually curated database of protein-protein interactions for mammalian TRP channels| publisher = | pages = | language = | archiveurl = | archivedate = | quote = }}


{{Ion channels}}
{{Ligand-gated ion channels}}

[[Category:Cell communication]]
[[Category:Electrophysiology]]
[[Category:Integral membrane proteins]]
[[Category:Ion channels]]
[[Category:Neurochemistry]]
[[Category:Protein families]]

[[ar:قناة شاردية]]
[[bg:Йонен канал]]
[[ca:Canal iònic]]
[[cs:Iontový kanál]]
[[da:Ionkanal]]
[[de:Ionenkanal]]
[[et:Ioonikanal]]
[[es:Canal iónico]]
[[fr:Canal ionique]]
[[ko:이온 통로]]
[[is:Jónahlið]]
[[it:Canale ionico]]
[[he:תעלת יונים]]
[[nl:Ionkanaal]]
[[ja:イオンチャネル]]
[[pl:Kanał jonowy]]
[[pt:Canal iônico]]
[[ru:Ионные каналы]]
[[simple:Ion channel]]
[[sl:Ionski kanalček]]
[[fi:Ionikanava]]
[[sv:Jonkanal]]
[[uk:Іонні канали]]
[[zh:离子通道]]
[[Category:2Fix]]