User:Ralf Stephan/Sandbox 2: Difference between revisions

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'''Ion channels''' are membrane proteins that catalyze the passive transport of ions through the cell membrane. Most ion channels are specific to an ion, like the [[natrium channels]], or the [[chloride channels]]. Some, like the [[TRP channels]], let through a bunch of cations. Another property of ion channels is that they can be either driven by voltage or concentration gradients, or they can be gated (by voltage, ligands, touch and other sensory signal). Finally, ion channels are the fastest of all membrane transporters, with 10^6 to 10^8 transported units per second versus 10^2 to 10^4 molecules per second for porters/carriers, or 10^0 to 10^3 for ATP-driven pumps.
<applet load='1xyz' />
 
'''Test''' <ref>Ref</ref>
== Classification ==
<applet load='1xyz' />
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]], but also from non-ribosomally synthesized channels like [[gramicidin]], [[polyglutamine]] or [[digitoxin]]. All these proteins are '''passive''' transport proteins.
<references/>
 
== Available structures ==
Membrane transport proteins are notoriously difficult to crystallize while in a working state. So, it's no surprise that there are preciously few structure data for ion channels. At the moment, the following ion channels have been at least partly resolved:
* the [[voltage-gated passium channel]] from ''Streptomyces lividans'' with the structures [[1bl8]], [[1k4c]], [[1k4d]]
* the [[calcium-gated potassium channel mthK]] from ''Methanobacterium thermoautotrophicum'' ([[1lnq]])
* the [[voltage-gated potassium channel]] K<sub>v</sub>AP from ''Aeropyrum pernix'' ([[1onq]])
* a [[potassium channel]] from ''Burkholderia pseudomallei'' ([[1p7b]])
* [[aquaporins]] from several species:
** ''Methanobacterium thermoautotrophicum'' (aqpM, [[2evu]], [[2f2c]])
** ''E.&nbsp;coli'' K12 (Aquaporin Z, [[1r2c]], [[2abm]])
** the [[glycerol uptake facilitator]] from ''E.&nbsp;coli'' K12 ([[1fx8]])
** ''Homo sapiens'' (AQP-1, [[1fqy]], [[1ih5]])
** ''Bos taurus'' (Aquaporin-0, [[1ymg]], [[2b6p]])
* the [[ammonia transporter]] from ''E.&nbsp;coli'' K12 ([[1u7g]], [[1xqf]], [[2ns1]], [[2nuu]])
* the [[ammonium transporter]] from ''Archaeoglobus fulgidus'' ([[2b2f]])
* the small-conductance [[mechanosensitive channel]] from ''E.&nbsp;coli'' K12 ([[2oau]])
* human [[phospholamban]] ([[1zll]])
== Weblinks ==
*[http://www.tcdb.org/ The TCDB database]
*[http://www.tcdb.org/tcdb/subclass2.php?tc=1.A TCDB: 1.A α-Type channels]
*[http://www.tcdb.org/pdb_structure.php TCDB: Transport proteins with PDB structures]

Latest revision as of 11:28, 21 February 2009

PDB ID 1xyz

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Test [1]

PDB ID 1xyz

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  1. ↑ Ref
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