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== Ion channel types ==
== Ion channel types ==
Most ion channels are specific to an ion, like the '''sodium channels''', or the '''potassium channels'''.<br />
Most ion channels are specific to an ion, like the '''sodium channels''', or the '''potassium channels'''<ref>PMID:19165895</ref>.<br />
'''TRP channels''' let through various cations.<br />
'''TRP channels''' let through various cations<ref>PMID:17579562</ref>.<br />
Another property of ion channels is that they can be either driven by voltage or by concentration gradients, or they can be gated (by voltage, ligands, touch and other sensory signal). '''Potassium channels''' (KCh) are subdivided to voltage-gated KCh and calcium-dependent KCh.  The latter are subdivided into high- (BK, LKCa), intermediate- and small-conductance KCh (human SK1, rat SK2, SKCa).  See [[Potassium Channel|Potassium channels]].<br />
Another property of ion channels is that they can be either driven by voltage or by concentration gradients, or they can be gated (by voltage, ligands, touch and other sensory signal). '''Potassium channels''' (KCh) are subdivided to voltage-gated KCh and calcium-dependent KCh.  The latter are subdivided into high- (BK, LKCa), intermediate- and small-conductance KCh (human SK1, rat SK2, SKCa).  See [[Potassium Channel|Potassium channels]].<br />
'''MthK''' is a calcium-dependent potassium channel from ''Methanobacterium thermoautrophicum''.<br />
'''MthK''' is a calcium-dependent potassium channel from ''Methanobacterium thermoautrophicum''<ref>PMID:16735753</ref>.<br />
'''MscL''' and '''MscS''' are large- and small-conductance mechanosensitive channels which protect bacteria from osmotic shock by allowing ions to flow across the cell membrane. See [[Mechanosensitive channels: opening and closing]].<br />
'''MscL''' and '''MscS''' are large- and small-conductance mechanosensitive channels which protect bacteria from osmotic shock by allowing ions to flow across the cell membrane<ref>PMID:12046893</ref>. See [[Mechanosensitive channels: opening and closing]].<br />
'''Voltage-Dependent Calcium Channels''' (VDCC) allow calcium ions to enter the cell resulting in muscle contraction, neuron excitation or hormone release.  VDCC are composed of several subunits and are named as a Cav gene product.  See [[Voltage-gated calcium channels]].<br />
'''Voltage-Dependent Calcium Channels''' (VDCC) allow calcium ions to enter the cell resulting in muscle contraction, neuron excitation or hormone release.  VDCC are composed of several subunits and are named as a Cav gene product<ref>PMID:16096350</ref>.  See [[Voltage-gated calcium channels]].<br />
There are also '''Voltage-Dependent Anion Channels''' (VDAC).<br />
There are also '''Voltage-Dependent Anion Channels''' (VDAC)<ref>PMID:16787253</ref>.<br />
'''Chloride ion channels''' (ClCh) are involved in maintaining pH, volume homeostasis and more.  See [[Chloride Ion Channel]], [[User:Laura Fountain/Chloride Ion Channel]] and [[Chloride Intracellular Channel Protein 2]]<br />
'''Chloride ion channels''' (ClCh) are involved in maintaining pH, volume homeostasis and more.  See [[Chloride Ion Channel]], [[User:Laura Fountain/Chloride Ion Channel]] and [[Chloride Intracellular Channel Protein 2]]<br />
'''Ligand-Gated Ion Channels''' (LGIC) open or close when binding a ligand like a neurotransmitter.<br />
'''Ligand-Gated Ion Channels''' (LGIC) open or close when binding a ligand like a neurotransmitter<ref>PMID:15288758</ref>.<br />
'''Cyclic Nucleotide-Gated channels''' (CNGC) conduct cations upon binding of cAMP or cGMP.<br />
'''Cyclic Nucleotide-Gated channels''' (CNGC) conduct cations upon binding of cAMP or cGMP<ref>PMID:12087135</ref>.<br />
'''Acid-Sensitive channels''' (ASC) conduct cations upon binding of acid.<br />
'''Acid-Sensitive channels''' (ASC) conduct cations upon binding of acid<ref>PMID:19655111</ref>.<br />
'''Glycerol facilitator''' (GlpF) is a protein channel which transports glycerol across the cell membrane of ''E. coli''.<br />
'''Glycerol facilitator''' (GlpF) is a protein channel which transports glycerol across the cell membrane of ''E. coli''<ref>PMID:12948772</ref>.<br />
Other ion channel proteins are the aquaporins, annexin V, gramicidin, antiamoebin, trichotoxin, peptaibol and the glutamate receptor.  Specific details in:<br />
Other ion channel proteins are the aquaporins, annexin V, gramicidin, antiamoebin, trichotoxin, peptaibol and the glutamate receptor.  Specific details in:<br />
*[[Proton Channels]], <br />
*[[Proton Channels]], <br />
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== Classification ==
== Classification ==
TCDB, the most sophisticated classification of transport proteins to date, classify ion channels as a heterogenous subset of all '''&alpha;-type channels''', whose singular property is to consist mainly of [[alpha helix|&alpha;-helices]] that span the membrane. They are distinct in this from the beta-barrel [[porins]] and the [[pore-forming toxins]], as well as from non-ribosomally synthesized channels like [[gramicidin]], [[polyglutamine]] or [[digitoxin]]. All these proteins are '''passive''' transport proteins.
TCDB, the most sophisticated classification of transport proteins to date, classify ion channels as a heterogenous subset of all '''&alpha;-type channels''', whose singular property is to consist mainly of [[alpha helix|&alpha;-helices]] that span the membrane. They are distinct in this from the beta-barrel [[porins]] and the [[pore-forming toxins]], as well as from non-ribosomally synthesized channels like [[gramicidin]], [[polyglutamine]] or [[digitoxin]]. All these proteins are '''passive''' transport proteins.
== Disease ==
Mutations in sodium channel are involved in arrhythmia<ref>PMID:19377496</ref>, epilepsy<ref>PMID:16075041</ref>, Brugada syndrome and cardiac conduction disease<ref>PMID:18464934</ref>.


==Additional Resources==
==Additional Resources==

Revision as of 10:48, 31 March 2016

Template:STRUCTURE 1qrq

FunctionFunction

Ion channels are membrane proteins that catalyze the passive transport of ions through the cell membrane. Ion channels are the fastest of all membrane transporters, with 106 to 108 transported units per second versus 102 to 104 molecules per second for porters/carriers, or 100 to 103 for ATP-driven pumps.

Ion channel typesIon channel types

Most ion channels are specific to an ion, like the sodium channels, or the potassium channels[1].
TRP channels let through various cations[2].
Another property of ion channels is that they can be either driven by voltage or by concentration gradients, or they can be gated (by voltage, ligands, touch and other sensory signal). Potassium channels (KCh) are subdivided to voltage-gated KCh and calcium-dependent KCh. The latter are subdivided into high- (BK, LKCa), intermediate- and small-conductance KCh (human SK1, rat SK2, SKCa). See Potassium channels.
MthK is a calcium-dependent potassium channel from Methanobacterium thermoautrophicum[3].
MscL and MscS are large- and small-conductance mechanosensitive channels which protect bacteria from osmotic shock by allowing ions to flow across the cell membrane[4]. See Mechanosensitive channels: opening and closing.
Voltage-Dependent Calcium Channels (VDCC) allow calcium ions to enter the cell resulting in muscle contraction, neuron excitation or hormone release. VDCC are composed of several subunits and are named as a Cav gene product[5]. See Voltage-gated calcium channels.
There are also Voltage-Dependent Anion Channels (VDAC)[6].
Chloride ion channels (ClCh) are involved in maintaining pH, volume homeostasis and more. See Chloride Ion Channel, User:Laura Fountain/Chloride Ion Channel and Chloride Intracellular Channel Protein 2
Ligand-Gated Ion Channels (LGIC) open or close when binding a ligand like a neurotransmitter[7].
Cyclic Nucleotide-Gated channels (CNGC) conduct cations upon binding of cAMP or cGMP[8].
Acid-Sensitive channels (ASC) conduct cations upon binding of acid[9].
Glycerol facilitator (GlpF) is a protein channel which transports glycerol across the cell membrane of E. coli[10].
Other ion channel proteins are the aquaporins, annexin V, gramicidin, antiamoebin, trichotoxin, peptaibol and the glutamate receptor. Specific details in:

ClassificationClassification

TCDB, the most sophisticated classification of transport proteins to date, classify ion channels as a heterogenous subset of all α-type channels, whose singular property is to consist mainly of α-helices that span the membrane. They are distinct in this from the beta-barrel porins and the pore-forming toxins, as well as from non-ribosomally synthesized channels like gramicidin, polyglutamine or digitoxin. All these proteins are passive transport proteins.

DiseaseDisease

Mutations in sodium channel are involved in arrhythmia[11], epilepsy[12], Brugada syndrome and cardiac conduction disease[13].

Additional ResourcesAdditional Resources

For additional information, see: Membrane Channels & Pumps
For additional information, see: Hypertension & Congestive Heart Failure

3D structures of ion channels3D structures of ion channels

Updated on 31-March-2016

WeblinksWeblinks

ReferencesReferences

  1. ↑ Szewczyk A, Jarmuszkiewicz W, Kunz WS. Mitochondrial potassium channels. IUBMB Life. 2009 Feb;61(2):134-43. doi: 10.1002/iub.155. PMID:19165895 doi:http://dx.doi.org/10.1002/iub.155
  2. ↑ Venkatachalam K, Montell C. TRP channels. Annu Rev Biochem. 2007;76:387-417. PMID:17579562 doi:http://dx.doi.org/10.1146/annurev.biochem.75.103004.142819
  3. ↑ Zadek B, Nimigean CM. Calcium-dependent gating of MthK, a prokaryotic potassium channel. J Gen Physiol. 2006 Jun;127(6):673-85. PMID:16735753 doi:http://dx.doi.org/10.1085/jgp.200609534
  4. ↑ Kloda A, Martinac B. Mechanosensitive channels of bacteria and archaea share a common ancestral origin. Eur Biophys J. 2002 Mar;31(1):14-25. PMID:12046893
  5. ↑ Lacinova L. Voltage-dependent calcium channels. Gen Physiol Biophys. 2005 Jun;24 Suppl 1:1-78. PMID:16096350
  6. ↑ Shoshan-Barmatz V, Israelson A, Brdiczka D, Sheu SS. The voltage-dependent anion channel (VDAC): function in intracellular signalling, cell life and cell death. Curr Pharm Des. 2006;12(18):2249-70. PMID:16787253
  7. ↑ Keramidas A, Moorhouse AJ, Schofield PR, Barry PH. Ligand-gated ion channels: mechanisms underlying ion selectivity. Prog Biophys Mol Biol. 2004 Oct;86(2):161-204. PMID:15288758 doi:http://dx.doi.org/10.1016/j.pbiomolbio.2003.09.002
  8. ↑ Kaupp UB, Seifert R. Cyclic nucleotide-gated ion channels. Physiol Rev. 2002 Jul;82(3):769-824. PMID:12087135 doi:http://dx.doi.org/10.1152/physrev.00008.2002
  9. ↑ Holzer P. Acid-sensitive ion channels and receptors. Handb Exp Pharmacol. 2009;(194):283-332. doi: 10.1007/978-3-540-79090-7_9. PMID:19655111 doi:http://dx.doi.org/10.1007/978-3-540-79090-7_9
  10. ↑ Stroud RM, Miercke LJ, O'Connell J, Khademi S, Lee JK, Remis J, Harries W, Robles Y, Akhavan D. Glycerol facilitator GlpF and the associated aquaporin family of channels. Curr Opin Struct Biol. 2003 Aug;13(4):424-31. PMID:12948772
  11. ↑ Ruan Y, Liu N, Priori SG. Sodium channel mutations and arrhythmias. Nat Rev Cardiol. 2009 May;6(5):337-48. doi: 10.1038/nrcardio.2009.44. PMID:19377496 doi:http://dx.doi.org/10.1038/nrcardio.2009.44
  12. ↑ Meisler MH, Kearney JA. Sodium channel mutations in epilepsy and other neurological disorders. J Clin Invest. 2005 Aug;115(8):2010-7. PMID:16075041 doi:http://dx.doi.org/10.1172/JCI25466
  13. ↑ Watanabe H, Koopmann TT, Le Scouarnec S, Yang T, Ingram CR, Schott JJ, Demolombe S, Probst V, Anselme F, Escande D, Wiesfeld AC, Pfeufer A, Kaab S, Wichmann HE, Hasdemir C, Aizawa Y, Wilde AA, Roden DM, Bezzina CR. Sodium channel beta1 subunit mutations associated with Brugada syndrome and cardiac conduction disease in humans. J Clin Invest. 2008 Jun;118(6):2260-8. doi: 10.1172/JCI33891. PMID:18464934 doi:http://dx.doi.org/10.1172/JCI33891

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