Langbahn Team – Weltmeisterschaft

Potassium channel

Potassium channel Kv1.2, structure in a membrane-like environment. Calculated hydrocarbon boundaries of the lipid bilayer are indicated by red and blue lines.

Potassium channels are the most widely distributed type of ion channel found in virtually all organisms.[1] 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.[2][3]

Function

Potassium channels function to conduct potassium ions down their electrochemical gradient, doing so both rapidly (up to the diffusion rate of K+ ions in bulk water) and selectively (excluding, most notably, sodium despite the sub-angstrom difference in ionic radius).[4] Biologically, these channels act to set or reset the resting potential in many cells. In excitable cells, such as neurons, the delayed counterflow of potassium ions shapes the action potential.

By contributing to the regulation of the cardiac action potential duration in cardiac muscle, malfunction of potassium channels may cause life-threatening arrhythmias. Potassium channels may also be involved in maintaining vascular tone.

They also regulate cellular processes such as the secretion of hormones (e.g., insulin release from beta-cells in the pancreas) so their malfunction can lead to diseases (such as diabetes).

Some toxins, such as dendrotoxin, are potent because they block potassium channels.[5]

Types

There are four major classes of potassium channels:

The following table contains a comparison of the major classes of potassium channels with representative examples (for a complete list of channels within each class, see the respective class pages).

For more examples of pharmacological modulators of potassium channels, see potassium channel blocker and potassium channel opener.

Potassium channel classes, function, and pharmacology.[6]
Class Subclasses Function Blockers Activators
Calcium-activated
6T & 1P
  • inhibition in response to rising intracellular calcium
 [citation needed]
Inwardly rectifying
2T & 1P
  • recycling and secretion of potassium in nephrons
  • final repolarization phase and stabilising the resting potential of the action potential in cardiac myocytes[16]
  • mediate the inhibitory effect of many GPCRs
  • close when ATP is high to promote insulin secretion
 [citation needed]
Tandem pore domain
4T & 2P 		[citation needed]
Voltage-gated
6T & 1P

Structure

Top view of a potassium channel with potassium ions (purple) moving through the pore (in the center). (PDB: 1BL8​)

Potassium channels have a tetrameric structure in which four identical protein subunits associate to form a fourfold symmetric (C4) complex arranged around a central ion conducting pore (i.e., a homotetramer). Alternatively four related but not identical protein subunits may associate to form heterotetrameric complexes with pseudo C4 symmetry. All potassium channel subunits have a distinctive pore-loop structure that lines the top of the pore and is responsible for potassium selective permeability.

There are over 80 mammalian genes that encode potassium channel subunits. However potassium channels found in bacteria are amongst the most studied of ion channels, in terms of their molecular structure. Using X-ray crystallography,[55][56] profound insights have been gained into how potassium ions pass through these channels and why (smaller) sodium ions do not.[57] The 2003 Nobel Prize for Chemistry was awarded to Rod MacKinnon for his pioneering work in this area.[58]

Selectivity filter

Crystallographic structure of the bacterial KcsA potassium channel (PDB: 1K4C​).[59] In this figure, only two of the four subunits of the tetramer are displayed for the sake of clarity. The protein is displayed as a green cartoon diagram. In addition backbone carbonyl groups and threonine sidechain protein atoms (oxygen = red, carbon = green) are displayed. Finally potassium ions (occupying the S2 and S4 sites) and the oxygen atoms of water molecules (S1 and S3) are depicted as purple and red spheres respectively.

Potassium ion channels remove the hydration shell from the ion when it enters the selectivity filter. The selectivity filter is formed by a five residue sequence, TVGYG, termed the signature sequence, within each of the four subunits. This signature sequence is within a loop between the pore helix and TM2/6, historically termed the P-loop. This signature sequence is highly conserved, with the exception that a valine residue in prokaryotic potassium channels is often substituted with an isoleucine residue in eukaryotic channels. This sequence adopts a unique main chain structure, structurally analogous to a nest protein structural motif. The four sets of electronegative carbonyl oxygen atoms are aligned toward the center of the filter pore and form a square antiprism similar to a water-solvating shell around each potassium binding site. The distance between the carbonyl oxygens and potassium ions in the binding sites of the selectivity filter is the same as between water oxygens in the first hydration shell and a potassium ion in water solution, providing an energetically-favorable route for de-solvation of the ions. Sodium ions, however, are too small to fill the space between the carbonyl oxygen atoms. Thus, it is energetically favorable for sodium ions to remain bound with water molecules in the extracellular space, rather than to pass through the potassium-selective ion pore.[60] This width appears to be maintained by hydrogen bonding and van der Waals forces within a sheet of aromatic amino acid residues surrounding the selectivity filter.[55][61] The selectivity filter opens towards the extracellular solution, exposing four carbonyl oxygens in a glycine residue (Gly79 in KcsA). The next residue toward the extracellular side of the protein is the negatively charged Asp80 (KcsA). This residue together with the five filter residues form the pore that connects the water-filled cavity in the center of the protein with the extracellular solution.[62]

Selectivity mechanism

The mechanism of potassium channel selectivity remains under continued debate. The carbonyl oxygens are strongly electro-negative and cation-attractive. The filter can accommodate potassium ions at 4 sites usually labelled S1 to S4 starting at the extracellular side. In addition, one ion can bind in the cavity at a site called SC or one or more ions at the extracellular side at more or less well-defined sites called S0 or Sext. Several different occupancies of these sites are possible. Since the X-ray structures are averages over many molecules, it is, however, not possible to deduce the actual occupancies directly from such a structure. In general, there is some disadvantage due to electrostatic repulsion to have two neighboring sites occupied by ions. Proposals for the mechanism of selectivity have been made based on molecular dynamics simulations,[63] toy models of ion binding,[64] thermodynamic calculations,[65] topological considerations,[66][67] and structural differences[68] between selective and non-selective channels.

The mechanism for ion translocation in KcsA has been studied extensively by theoretical calculations and simulation.[62][69] The prediction of an ion conduction mechanism in which the two doubly occupied states (S1, S3) and (S2, S4) play an essential role has been affirmed by both techniques. Molecular dynamics (MD) simulations suggest the two extracellular states, Sext and S0, reflecting ions entering and leaving the filter, also are important actors in ion conduction.

Hydrophobic region

This region neutralizes the environment around the potassium ion so that it is not attracted to any charges. In turn, it speeds up the reaction.

Central cavity

A central pore, 10 Å wide, is located near the center of the transmembrane channel, where the energy barrier is highest for the transversing ion due to the hydrophobity of the channel wall. The water-filled cavity and the polar C-terminus of the pore helices ease the energetic barrier for the ion. Repulsion by preceding multiple potassium ions is thought to aid the throughput of the ions. The presence of the cavity can be understood intuitively as one of the channel's mechanisms for overcoming the dielectric barrier, or repulsion by the low-dielectric membrane, by keeping the K+ ion in a watery, high-dielectric environment.

Regulation

Graphical representation of open and shut potassium channels (PDB: 1lnq​ and PDB: 1k4c​). Two simple bacterial channels are shown to compare the "open" channel structure on the right with the "closed" structure on the left. At top is the filter (selects potassium ions), and at bottom is the gating domain (controls opening and closing of channel).

The flux of ions through the potassium channel pore is regulated by two related processes, termed gating and inactivation. Gating is the opening or closing of the channel in response to stimuli, while inactivation is the rapid cessation of current from an open potassium channel and the suppression of the channel's ability to resume conducting. While both processes serve to regulate channel conductance, each process may be mediated by a number of mechanisms.

Generally, gating is thought to be mediated by additional structural domains which sense stimuli and in turn open the channel pore. These domains include the RCK domains of BK channels,[70][71][72] and voltage sensor domains of voltage gated K+ channels. These domains are thought to respond to the stimuli by physically opening the intracellular gate of the pore domain, thereby allowing potassium ions to traverse the membrane. Some channels have multiple regulatory domains or accessory proteins, which can act to modulate the response to stimulus. While the mechanisms continue to be debated, there are known structures of a number of these regulatory domains, including RCK domains of prokaryotic[73][74][75] and eukaryotic[70][71][72] channels, pH gating domain of KcsA,[76] cyclic nucleotide gating domains,[77] and voltage gated potassium channels.[78][79]

N-type inactivation is typically the faster inactivation mechanism, and is termed the "ball and chain" model.[80] N-type inactivation involves interaction of the N-terminus of the channel, or an associated protein, which interacts with the pore domain and occludes the ion conduction pathway like a "ball". Alternatively, C-type inactivation is thought to occur within the selectivity filter itself, where structural changes within the filter render it non-conductive. There are a number of structural models of C-type inactivated K+ channel filters,[81][82][83] although the precise mechanism remains unclear.

Pharmacology

Blockers

Main article: Potassium channel blocker

Potassium channel blockers inhibit the flow of potassium ions through the channel. They either compete with potassium binding within the selectivity filter or bind outside the filter to occlude ion conduction. An example of one of these competitors is quaternary ammonium ions, which bind at the extracellular face[84][85] or central cavity of the channel.[86] For blocking from the central cavity quaternary ammonium ions are also known as open channel blockers, as binding classically requires the prior opening of the cytoplasmic gate.[87]

Barium ions can also block potassium channel currents,[88][89] by binding with high affinity within the selectivity filter.[90][91][92][93] This tight binding is thought to underlie barium toxicity by inhibiting potassium channel activity in excitable cells.

Medically potassium channel blockers, such as 4-aminopyridine and 3,4-diaminopyridine, have been investigated for the treatment of conditions such as multiple sclerosis.[49] Off target drug effects can lead to drug induced Long QT syndrome, a potentially life-threatening condition. This is most frequently due to action on the hERG potassium channel in the heart. Accordingly, all new drugs are preclinically tested for cardiac safety.

Activators

Main article: Potassium channel opener

Muscarinic potassium channel

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.
See also: G protein-coupled inwardly-rectifying potassium channel

Some types of potassium channels are activated by muscarinic receptors and these are called muscarinic potassium channels (IKACh). These channels are a heterotetramer composed of two GIRK1 and two GIRK4 subunits.[94][95] Examples are potassium channels in the heart, which, when activated by parasympathetic signals through M2 muscarinic receptors, cause an outward current of potassium, which slows down the heart rate.[96][97]

In fine art

Roderick MacKinnon commissioned Birth of an Idea, a 5-foot (1.5 m) tall sculpture based on the KcsA potassium channel.[98] The artwork contains a wire object representing the channel's interior with a blown glass object representing the main cavity of the channel structure.

See also

References

  1. ^ Littleton JT, Ganetzky B (April 2000). "Ion channels and synaptic organization: analysis of the Drosophila genome". Neuron. 26 (1): 35–43. doi:10.1016/S0896-6273(00)81135-6. PMID 10798390. S2CID 5694563.
  2. ^ Hille, Bertil (2001). "Chapter 5: Potassium Channels and Chloride Channels". Ion channels of excitable membranes. Sunderland, Mass: Sinauer. pp. 131–168. ISBN 978-0-87893-321-1.
  3. ^ Jessell TM, Kandel ER, Schwartz JH (2000). "Chapter 6: Ion Channels". Principles of Neural Science (4th ed.). New York: McGraw-Hill. pp. 105–124. ISBN 978-0-8385-7701-1.
  4. ^ Lim C, Dudev T (2016). "Roles and Transport of Sodium and Potassium in Plants". In Sigel A, Sigel H, Sigel RK (eds.). The Alkali Metal Ions: Their Role for Life. Metal Ions in Life Sciences. Vol. 16. Springer. pp. 325–347. doi:10.1007/978-3-319-21756-7_9. ISBN 978-3-319-21755-0. PMID 26860305. {{cite book}}: |journal= ignored (help)
  5. ^ indirectly cited from reference number 3,4,5,6 in Rehm H, Lazdunski M (July 1988). "Purification and subunit structure of a putative K+-channel protein identified by its binding properties for dendrotoxin I". Proceedings of the National Academy of Sciences of the United States of America. 85 (13): 4919–4923. Bibcode:1988PNAS...85.4919R. doi:10.1073/pnas.85.13.4919. PMC 280549. PMID 2455300.
  6. ^ a b c d e f g h i j k l m n Rang, HP (2015). Pharmacology (8 ed.). Edinburgh: Churchill Livingstone. p. 59. ISBN 978-0-443-07145-4.
  7. ^ Thompson J, Begenisich T (May 2000). "Electrostatic interaction between charybdotoxin and a tetrameric mutant of Shaker K(+) channels". Biophysical Journal. 78 (5): 2382–2391. Bibcode:2000BpJ....78.2382T. doi:10.1016/S0006-3495(00)76782-8. PMC 1300827. PMID 10777734.
  8. ^ Naranjo D, Miller C (January 1996). "A strongly interacting pair of residues on the contact surface of charybdotoxin and a Shaker K+ channel". Neuron. 16 (1): 123–130. doi:10.1016/S0896-6273(00)80029-X. PMID 8562075. S2CID 16794677.
  9. ^ Yu M, Liu SL, Sun PB, Pan H, Tian CL, Zhang LH (January 2016). "Peptide toxins and small-molecule blockers of BK channels". Acta Pharmacologica Sinica. 37 (1): 56–66. doi:10.1038/aps.2015.139. PMC 4722972. PMID 26725735.
  10. ^ Candia S, Garcia ML, Latorre R (August 1992). "Mode of action of iberiotoxin, a potent blocker of the large conductance Ca(2+)-activated K+ channel". Biophysical Journal. 63 (2): 583–590. Bibcode:1992BpJ....63..583C. doi:10.1016/S0006-3495(92)81630-2. PMC 1262182. PMID 1384740.
  11. ^ Stocker M, Krause M, Pedarzani P (April 1999). "An apamin-sensitive Ca2+-activated K+ current in hippocampal pyramidal neurons". Proceedings of the National Academy of Sciences of the United States of America. 96 (8): 4662–4667. Bibcode:1999PNAS...96.4662S. doi:10.1073/pnas.96.8.4662. PMC 16389. PMID 10200319.
  12. ^ McLeod JF, Leempoels JM, Peng SX, Dax SL, Myers LJ, Golder FJ (November 2014). "GAL-021, a new intravenous BKCa-channel blocker, is well tolerated and stimulates ventilation in healthy volunteers". British Journal of Anaesthesia. 113 (5): 875–883. doi:10.1093/bja/aeu182. PMID 24989775.
  13. ^ Dopico AM, Bukiya AN, Kuntamallappanavar G, Liu J (2016). "Modulation of BK Channels by Ethanol". International Review of Neurobiology. 128: 239–279. doi:10.1016/bs.irn.2016.03.019. ISBN 9780128036198. PMC 5257281. PMID 27238266.
  14. ^ a b Patnaik, Pradyot (2003). Handbook of inorganic chemicals. McGraw-Hill. pp. 77–78. ISBN 978-0-07-049439-8.
  15. ^ Sackin H, Syn S, Palmer LG, Choe H, Walters DE (February 2001). "Regulation of ROMK by extracellular cations". Biophysical Journal. 80 (2): 683–697. Bibcode:2001BpJ....80..683S. doi:10.1016/S0006-3495(01)76048-1. PMC 1301267. PMID 11159436.
  16. ^ Dhamoon AS, Jalife J (March 2005). "The inward rectifier current (IK1) controls cardiac excitability and is involved in arrhythmogenesis". Heart Rhythm. 2 (3): 316–324. doi:10.1016/j.hrthm.2004.11.012. PMID 15851327.
  17. ^ a b c d e f Swale DR, Kharade SV, Denton JS (April 2014). "Cardiac and renal inward rectifier potassium channel pharmacology: emerging tools for integrative physiology and therapeutics". Current Opinion in Pharmacology. 15: 7–15. doi:10.1016/j.coph.2013.11.002. PMC 4097192. PMID 24721648.
  18. ^ Xynogalos P, Seyler C, Scherer D, Koepple C, Scholz EP, Thomas D, et al. (December 2014). "Class III antiarrhythmic drug dronedarone inhibits cardiac inwardly rectifying Kir2.1 channels through binding at residue E224". Naunyn-Schmiedeberg's Archives of Pharmacology. 387 (12): 1153–1161. doi:10.1007/s00210-014-1045-6. PMID 25182566. S2CID 10575229.
  19. ^ Koepple C, Scherer D, Seyler C, Scholz E, Thomas D, Katus HA, Zitron E (May 2017). "Dual Mechanism for Inhibition of Inwardly Rectifying Kir2.x Channels by Quinidine Involving Direct Pore Block and PIP2-interference". The Journal of Pharmacology and Experimental Therapeutics. 361 (2): 209–218. doi:10.1124/jpet.116.238287. PMID 28188270. S2CID 206502631.
  20. ^ Caballero R, Dolz-Gaitón P, Gómez R, Amorós I, Barana A, González de la Fuente M, et al. (August 2010). "Flecainide increases Kir2.1 currents by interacting with cysteine 311, decreasing the polyamine-induced rectification". Proceedings of the National Academy of Sciences of the United States of America. 107 (35): 15631–15636. Bibcode:2010PNAS..10715631C. doi:10.1073/pnas.1004021107. PMC 2932566. PMID 20713726.
  21. ^ Kobayashi T, Washiyama K, Ikeda K (March 2006). "Inhibition of G protein-activated inwardly rectifying K+ channels by ifenprodil". Neuropsychopharmacology. 31 (3): 516–524. doi:10.1038/sj.npp.1300844. PMID 16123769.
  22. ^ Soeda F, Fujieda Y, Kinoshita M, Shirasaki T, Takahama K (May 2016). "Centrally acting non-narcotic antitussives prevent hyperactivity in mice: Involvement of GIRK channels". Pharmacology, Biochemistry, and Behavior. 144: 26–32. doi:10.1016/j.pbb.2016.02.006. PMID 26892760. S2CID 30118634.
  23. ^ Yamamoto G, Soeda F, Shirasaki T, Takahama K (April 2011). "[Is the GIRK channel a possible target in the development of a novel therapeutic drug of urinary disturbance?]". Yakugaku Zasshi. 131 (4): 523–532. doi:10.1248/yakushi.131.523. PMID 21467791.
  24. ^ Kawaura K, Honda S, Soeda F, Shirasaki T, Takahama K (May 2010). "[Novel antidepressant-like action of drugs possessing GIRK channel blocking action in rats]". Yakugaku Zasshi. 130 (5): 699–705. doi:10.1248/yakushi.130.699. PMID 20460867.
  25. ^ Jin W, Lu Z (September 1998). "A novel high-affinity inhibitor for inward-rectifier K+ channels". Biochemistry. 37 (38): 13291–13299. doi:10.1021/bi981178p. PMID 9748337.
  26. ^ Kawaura K, Ogata Y, Inoue M, Honda S, Soeda F, Shirasaki T, Takahama K (December 2009). "The centrally acting non-narcotic antitussive tipepidine produces antidepressant-like effect in the forced swimming test in rats" (PDF). Behavioural Brain Research. 205 (1): 315–318. doi:10.1016/j.bbr.2009.07.004. PMID 19616036. S2CID 29236491.
  27. ^ Kaufmann K, Romaine I, Days E, Pascual C, Malik A, Yang L, et al. (September 2013). "ML297 (VU0456810), the first potent and selective activator of the GIRK potassium channel, displays antiepileptic properties in mice". ACS Chemical Neuroscience. 4 (9): 1278–1286. doi:10.1021/cn400062a. PMC 3778424. PMID 23730969.
  28. ^ Serrano-Martín X, Payares G, Mendoza-León A (December 2006). "Glibenclamide, a blocker of K+(ATP) channels, shows antileishmanial activity in experimental murine cutaneous leishmaniasis". Antimicrobial Agents and Chemotherapy. 50 (12): 4214–4216. doi:10.1128/AAC.00617-06. PMC 1693980. PMID 17015627.
  29. ^ Lawrence CL, Proks P, Rodrigo GC, Jones P, Hayabuchi Y, Standen NB, Ashcroft FM (August 2001). "Gliclazide produces high-affinity block of KATP channels in mouse isolated pancreatic beta cells but not rat heart or arterial smooth muscle cells". Diabetologia. 44 (8): 1019–1025. doi:10.1007/s001250100595. PMID 11484080.
  30. ^ a b c d e f Enyedi P, Czirják G (April 2010). "Molecular background of leak K+ currents: two-pore domain potassium channels". Physiological Reviews. 90 (2): 559–605. doi:10.1152/physrev.00029.2009. PMID 20393194. S2CID 9358238.
  31. ^ a b c d e f Lotshaw DP (2007). "Biophysical, pharmacological, and functional characteristics of cloned and native mammalian two-pore domain K+ channels". Cell Biochemistry and Biophysics. 47 (2): 209–256. doi:10.1007/s12013-007-0007-8. PMID 17652773. S2CID 12759521.
  32. ^ Fink M, Lesage F, Duprat F, Heurteaux C, Reyes R, Fosset M, Lazdunski M (June 1998). "A neuronal two P domain K+ channel stimulated by arachidonic acid and polyunsaturated fatty acids". The EMBO Journal. 17 (12): 3297–3308. doi:10.1093/emboj/17.12.3297. PMC 1170668. PMID 9628867.
  33. ^ Goldstein SA, Bockenhauer D, O'Kelly I, Zilberberg N (March 2001). "Potassium leak channels and the KCNK family of two-P-domain subunits". Nature Reviews. Neuroscience. 2 (3): 175–184. doi:10.1038/35058574. PMID 11256078. S2CID 9682396.
  34. ^ Sano Y, Inamura K, Miyake A, Mochizuki S, Kitada C, Yokoi H, et al. (July 2003). "A novel two-pore domain K+ channel, TRESK, is localized in the spinal cord". The Journal of Biological Chemistry. 278 (30): 27406–27412. doi:10.1074/jbc.M206810200. PMID 12754259.
  35. ^ Czirják G, Tóth ZE, Enyedi P (April 2004). "The two-pore domain K+ channel, TRESK, is activated by the cytoplasmic calcium signal through calcineurin". The Journal of Biological Chemistry. 279 (18): 18550–18558. doi:10.1074/jbc.M312229200. PMID 14981085.
  36. ^ Kindler CH, Yost CS, Gray AT (April 1999). "Local anesthetic inhibition of baseline potassium channels with two pore domains in tandem". Anesthesiology. 90 (4): 1092–1102. doi:10.1097/00000542-199904000-00024. PMID 10201682.
  37. ^ a b c Meadows HJ, Randall AD (March 2001). "Functional characterisation of human TASK-3, an acid-sensitive two-pore domain potassium channel". Neuropharmacology. 40 (4): 551–559. doi:10.1016/S0028-3908(00)00189-1. PMID 11249964. S2CID 20181576.
  38. ^ Kindler CH, Paul M, Zou H, Liu C, Winegar BD, Gray AT, Yost CS (July 2003). "Amide local anesthetics potently inhibit the human tandem pore domain background K+ channel TASK-2 (KCNK5)". The Journal of Pharmacology and Experimental Therapeutics. 306 (1): 84–92. doi:10.1124/jpet.103.049809. PMID 12660311. S2CID 1621972.
  39. ^ Punke MA, Licher T, Pongs O, Friederich P (June 2003). "Inhibition of human TREK-1 channels by bupivacaine". Anesthesia and Analgesia. 96 (6): 1665–1673. doi:10.1213/01.ANE.0000062524.90936.1F. PMID 12760993. S2CID 39630495.
  40. ^ Lesage F, Guillemare E, Fink M, Duprat F, Lazdunski M, Romey G, Barhanin J (March 1996). "TWIK-1, a ubiquitous human weakly inward rectifying K+ channel with a novel structure". The EMBO Journal. 15 (5): 1004–1011. doi:10.1002/j.1460-2075.1996.tb00437.x. PMC 449995. PMID 8605869.
  41. ^ Duprat F, Lesage F, Fink M, Reyes R, Heurteaux C, Lazdunski M (September 1997). "TASK, a human background K+ channel to sense external pH variations near physiological pH". The EMBO Journal. 16 (17): 5464–5471. doi:10.1093/emboj/16.17.5464. PMC 1170177. PMID 9312005.
  42. ^ Reyes R, Duprat F, Lesage F, Fink M, Salinas M, Farman N, Lazdunski M (November 1998). "Cloning and expression of a novel pH-sensitive two pore domain K+ channel from human kidney". The Journal of Biological Chemistry. 273 (47): 30863–30869. doi:10.1074/jbc.273.47.30863. PMID 9812978.
  43. ^ Meadows HJ, Benham CD, Cairns W, Gloger I, Jennings C, Medhurst AD, et al. (April 2000). "Cloning, localisation and functional expression of the human orthologue of the TREK-1 potassium channel". Pflügers Archiv. 439 (6): 714–722. doi:10.1007/s004240050997. PMID 10784345.
  44. ^ "UniProtKB - Q9NPC2 (KCNK9_HUMAN)". Uniprot. Retrieved 2019-05-29.
  45. ^ a b Kennard LE, Chumbley JR, Ranatunga KM, Armstrong SJ, Veale EL, Mathie A (March 2005). "Inhibition of the human two-pore domain potassium channel, TREK-1, by fluoxetine and its metabolite norfluoxetine". British Journal of Pharmacology. 144 (6): 821–829. doi:10.1038/sj.bjp.0706068. PMC 1576064. PMID 15685212.
  46. ^ Patel AJ, Honoré E, Lesage F, Fink M, Romey G, Lazdunski M (May 1999). "Inhalational anesthetics activate two-pore-domain background K+ channels". Nature Neuroscience. 2 (5): 422–426. doi:10.1038/8084. PMID 10321245. S2CID 23092576.
  47. ^ Gray AT, Zhao BB, Kindler CH, Winegar BD, Mazurek MJ, Xu J, et al. (June 2000). "Volatile anesthetics activate the human tandem pore domain baseline K+ channel KCNK5". Anesthesiology. 92 (6): 1722–1730. doi:10.1097/00000542-200006000-00032. PMID 10839924. S2CID 45487917.
  48. ^ Kirsch GE, Narahashi T (June 1978). "3,4-diaminopyridine. A potent new potassium channel blocker". Biophysical Journal. 22 (3): 507–512. Bibcode:1978BpJ....22..507K. doi:10.1016/s0006-3495(78)85503-9. PMC 1473482. PMID 667299.
  49. ^ a b Judge SI, Bever CT (July 2006). "Potassium channel blockers in multiple sclerosis: neuronal Kv channels and effects of symptomatic treatment". Pharmacology & Therapeutics. 111 (1): 224–259. doi:10.1016/j.pharmthera.2005.10.006. PMID 16472864.
  50. ^ Tiku PE, Nowell PT (December 1991). "Selective inhibition of K(+)-stimulation of Na,K-ATPase by bretylium". British Journal of Pharmacology. 104 (4): 895–900. doi:10.1111/j.1476-5381.1991.tb12523.x. PMC 1908819. PMID 1667290.
  51. ^ Hille B (May 1967). "The selective inhibition of delayed potassium currents in nerve by tetraethylammonium ion". The Journal of General Physiology. 50 (5): 1287–1302. doi:10.1085/jgp.50.5.1287. PMC 2225709. PMID 6033586.
  52. ^ Armstrong CM (October 1971). "Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons". The Journal of General Physiology. 58 (4): 413–437. doi:10.1085/jgp.58.4.413. PMC 2226036. PMID 5112659.
  53. ^ "Amiodarone". Drugbank. Retrieved 2019-05-28.
  54. ^ Rogawski MA, Bazil CW (July 2008). "New molecular targets for antiepileptic drugs: alpha(2)delta, SV2A, and K(v)7/KCNQ/M potassium channels". Current Neurology and Neuroscience Reports. 8 (4): 345–352. doi:10.1007/s11910-008-0053-7. PMC 2587091. PMID 18590620.
  55. ^ a b Doyle DA, Morais Cabral J, Pfuetzner RA, Kuo A, Gulbis JM, Cohen SL, et al. (April 1998). "The structure of the potassium channel: molecular basis of K+ conduction and selectivity". Science. 280 (5360): 69–77. Bibcode:1998Sci...280...69D. doi:10.1126/science.280.5360.69. PMID 9525859.
  56. ^ MacKinnon R, Cohen SL, Kuo A, Lee A, Chait BT (April 1998). "Structural conservation in prokaryotic and eukaryotic potassium channels". Science. 280 (5360): 106–109. Bibcode:1998Sci...280..106M. doi:10.1126/science.280.5360.106. PMID 9525854. S2CID 33907550.
  57. ^ Armstrong C (April 1998). "The vision of the pore". Science. 280 (5360): 56–57. doi:10.1126/science.280.5360.56. PMID 9556453. S2CID 35339674.
  58. ^ "The Nobel Prize in Chemistry 2003". The Nobel Foundation. Retrieved 2007-11-16.
  59. ^ Zhou Y, Morais-Cabral JH, Kaufman A, MacKinnon R (November 2001). "Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution". Nature. 414 (6859): 43–48. Bibcode:2001Natur.414...43Z. doi:10.1038/35102009. PMID 11689936. S2CID 205022645.
  60. ^ Lodish H, Berk A, Kaiser C, Krieger M, Bretscher A, Ploegh H, et al. (2016). Molecular Cell Biology (8th ed.). New York, NY: W. H. Freeman and Company. p. 499. ISBN 978-1-4641-8339-3.
  61. ^ Sauer DB, Zeng W, Raghunathan S, Jiang Y (October 2011). "Protein interactions central to stabilizing the K+ channel selectivity filter in a four-sited configuration for selective K+ permeation". Proceedings of the National Academy of Sciences of the United States of America. 108 (40): 16634–16639. Bibcode:2011PNAS..10816634S. doi:10.1073/pnas.1111688108. PMC 3189067. PMID 21933962.
  62. ^ a b Hellgren M, Sandberg L, Edholm O (March 2006). "A comparison between two prokaryotic potassium channels (KirBac1.1 and KcsA) in a molecular dynamics (MD) simulation study". Biophysical Chemistry. 120 (1): 1–9. doi:10.1016/j.bpc.2005.10.002. PMID 16253415.
  63. ^ Noskov SY, Roux B (February 2007). "Importance of hydration and dynamics on the selectivity of the KcsA and NaK channels". The Journal of General Physiology. 129 (2): 135–143. doi:10.1085/jgp.200609633. PMC 2154357. PMID 17227917.
  64. ^ Noskov SY, Bernèche S, Roux B (October 2004). "Control of ion selectivity in potassium channels by electrostatic and dynamic properties of carbonyl ligands". Nature. 431 (7010): 830–834. Bibcode:2004Natur.431..830N. doi:10.1038/nature02943. PMID 15483608. S2CID 4414885.
  65. ^ Varma S, Rempe SB (August 2007). "Tuning ion coordination architectures to enable selective partitioning". Biophysical Journal. 93 (4): 1093–1099. arXiv:physics/0608180. Bibcode:2007BpJ....93.1093V. doi:10.1529/biophysj.107.107482. PMC 1929028. PMID 17513348.
  66. ^ Thomas M, Jayatilaka D, Corry B (October 2007). "The predominant role of coordination number in potassium channel selectivity". Biophysical Journal. 93 (8): 2635–2643. Bibcode:2007BpJ....93.2635T. doi:10.1529/biophysj.107.108167. PMC 1989715. PMID 17573427.
  67. ^ Bostick DL, Brooks CL (May 2007). "Selectivity in K+ channels is due to topological control of the permeant ion's coordinated state". Proceedings of the National Academy of Sciences of the United States of America. 104 (22): 9260–9265. Bibcode:2007PNAS..104.9260B. doi:10.1073/pnas.0700554104. PMC 1890482. PMID 17519335.
  68. ^ Derebe MG, Sauer DB, Zeng W, Alam A, Shi N, Jiang Y (January 2011). "Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites". Proceedings of the National Academy of Sciences of the United States of America. 108 (2): 598–602. Bibcode:2011PNAS..108..598D. doi:10.1073/pnas.1013636108. PMC 3021048. PMID 21187421.
  69. ^ Morais-Cabral JH, Zhou Y, MacKinnon R (November 2001). "Energetic optimization of ion conduction rate by the K+ selectivity filter". Nature. 414 (6859): 37–42. Bibcode:2001Natur.414...37M. doi:10.1038/35102000. PMID 11689935. S2CID 4429890.
  70. ^ a b Yuan P, Leonetti MD, Pico AR, Hsiung Y, MacKinnon R (July 2010). "Structure of the human BK channel Ca2+-activation apparatus at 3.0 A resolution". Science. 329 (5988): 182–186. Bibcode:2010Sci...329..182Y. doi:10.1126/science.1190414. PMC 3022345. PMID 20508092.
  71. ^ a b Wu Y, Yang Y, Ye S, Jiang Y (July 2010). "Structure of the gating ring from the human large-conductance Ca(2+)-gated K(+) channel". Nature. 466 (7304): 393–397. Bibcode:2010Natur.466..393W. doi:10.1038/nature09252. PMC 2910425. PMID 20574420.
  72. ^ a b Jiang Y, Pico A, Cadene M, Chait BT, MacKinnon R (March 2001). "Structure of the RCK domain from the E. coli K+ channel and demonstration of its presence in the human BK channel". Neuron. 29 (3): 593–601. doi:10.1016/S0896-6273(01)00236-7. PMID 11301020. S2CID 17880955.
  73. ^ Jiang Y, Lee A, Chen J, Cadene M, Chait BT, MacKinnon R (May 2002). "Crystal structure and mechanism of a calcium-gated potassium channel". Nature. 417 (6888): 515–522. Bibcode:2002Natur.417..515J. doi:10.1038/417515a. PMID 12037559. S2CID 205029269.
  74. ^ Kong C, Zeng W, Ye S, Chen L, Sauer DB, Lam Y, et al. (December 2012). "Distinct gating mechanisms revealed by the structures of a multi-ligand gated K(+) channel". eLife. 1: e00184. doi:10.7554/eLife.00184. PMC 3510474. PMID 23240087.
  75. ^ Cao Y, Jin X, Huang H, Derebe MG, Levin EJ, Kabaleeswaran V, et al. (March 2011). "Crystal structure of a potassium ion transporter, TrkH". Nature. 471 (7338): 336–340. Bibcode:2011Natur.471..336C. doi:10.1038/nature09731. PMC 3077569. PMID 21317882.
  76. ^ Uysal S, Cuello LG, Cortes DM, Koide S, Kossiakoff AA, Perozo E (July 2011). "Mechanism of activation gating in the full-length KcsA K+ channel". Proceedings of the National Academy of Sciences of the United States of America. 108 (29): 11896–11899. Bibcode:2011PNAS..10811896U. doi:10.1073/pnas.1105112108. PMC 3141920. PMID 21730186.
  77. ^ Clayton GM, Silverman WR, Heginbotham L, Morais-Cabral JH (November 2004). "Structural basis of ligand activation in a cyclic nucleotide regulated potassium channel". Cell. 119 (5): 615–627. doi:10.1016/j.cell.2004.10.030. PMID 15550244. S2CID 14149494.
  78. ^ Jiang Y, Lee A, Chen J, Ruta V, Cadene M, Chait BT, MacKinnon R (May 2003). "X-ray structure of a voltage-dependent K+ channel". Nature. 423 (6935): 33–41. Bibcode:2003Natur.423...33J. doi:10.1038/nature01580. PMID 12721618. S2CID 4347957.
  79. ^ Long SB, Campbell EB, Mackinnon R (August 2005). "Crystal structure of a mammalian voltage-dependent Shaker family K+ channel". Science. 309 (5736): 897–903. Bibcode:2005Sci...309..897L. doi:10.1126/science.1116269. PMID 16002581. S2CID 6072007.
  80. ^ Antz C, Fakler B (August 1998). "Fast Inactivation of Voltage-Gated K(+) Channels: From Cartoon to Structure". News in Physiological Sciences. 13 (4): 177–182. doi:10.1152/physiologyonline.1998.13.4.177. PMID 11390785. S2CID 38134756.
  81. ^ Cheng WW, McCoy JG, Thompson AN, Nichols CG, Nimigean CM (March 2011). "Mechanism for selectivity-inactivation coupling in KcsA potassium channels". Proceedings of the National Academy of Sciences of the United States of America. 108 (13): 5272–5277. Bibcode:2011PNAS..108.5272C. doi:10.1073/pnas.1014186108. PMC 3069191. PMID 21402935.
  82. ^ Cuello LG, Jogini V, Cortes DM, Perozo E (July 2010). "Structural mechanism of C-type inactivation in K(+) channels". Nature. 466 (7303): 203–208. Bibcode:2010Natur.466..203C. doi:10.1038/nature09153. PMC 3033749. PMID 20613835.
  83. ^ Cuello LG, Jogini V, Cortes DM, Pan AC, Gagnon DG, Dalmas O, et al. (July 2010). "Structural basis for the coupling between activation and inactivation gates in K(+) channels". Nature. 466 (7303): 272–275. Bibcode:2010Natur.466..272C. doi:10.1038/nature09136. PMC 3033755. PMID 20613845.
  84. ^ Luzhkov VB, Aqvist J (February 2005). "Ions and blockers in potassium channels: insights from free energy simulations". Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics. 1747 (1): 109–120. doi:10.1016/j.bbapap.2004.10.006. PMID 15680245.
  85. ^ Luzhkov VB, Osterberg F, Aqvist J (November 2003). "Structure-activity relationship for extracellular block of K+ channels by tetraalkylammonium ions". FEBS Letters. 554 (1–2): 159–164. Bibcode:2003FEBSL.554..159L. doi:10.1016/S0014-5793(03)01117-7. PMID 14596932. S2CID 32031835.
  86. ^ Posson DJ, McCoy JG, Nimigean CM (February 2013). "The voltage-dependent gate in MthK potassium channels is located at the selectivity filter". Nature Structural & Molecular Biology. 20 (2): 159–166. doi:10.1038/nsmb.2473. PMC 3565016. PMID 23262489.
  87. ^ Choi KL, Mossman C, Aubé J, Yellen G (March 1993). "The internal quaternary ammonium receptor site of Shaker potassium channels". Neuron. 10 (3): 533–541. doi:10.1016/0896-6273(93)90340-w. PMID 8461140. S2CID 33361945.
  88. ^ Piasta KN, Theobald DL, Miller C (October 2011). "Potassium-selective block of barium permeation through single KcsA channels". The Journal of General Physiology. 138 (4): 421–436. doi:10.1085/jgp.201110684. PMC 3182450. PMID 21911483.
  89. ^ Neyton J, Miller C (November 1988). "Potassium blocks barium permeation through a calcium-activated potassium channel". The Journal of General Physiology. 92 (5): 549–567. doi:10.1085/jgp.92.5.549. PMC 2228918. PMID 3235973.
  90. ^ Lockless SW, Zhou M, MacKinnon R (May 2007). "Structural and thermodynamic properties of selective ion binding in a K+ channel". PLOS Biology. 5 (5): e121. doi:10.1371/journal.pbio.0050121. PMC 1858713. PMID 17472437.
  91. ^ Jiang Y, MacKinnon R (March 2000). "The barium site in a potassium channel by x-ray crystallography". The Journal of General Physiology. 115 (3): 269–272. doi:10.1085/jgp.115.3.269. PMC 2217209. PMID 10694255.
  92. ^ Lam YL, Zeng W, Sauer DB, Jiang Y (August 2014). "The conserved potassium channel filter can have distinct ion binding profiles: structural analysis of rubidium, cesium, and barium binding in NaK2K". The Journal of General Physiology. 144 (2): 181–192. doi:10.1085/jgp.201411191. PMC 4113894. PMID 25024267.
  93. ^ Guo R, Zeng W, Cui H, Chen L, Ye S (August 2014). "Ionic interactions of Ba2+ blockades in the MthK K+ channel". The Journal of General Physiology. 144 (2): 193–200. doi:10.1085/jgp.201411192. PMC 4113901. PMID 25024268.
  94. ^ Krapivinsky G, Gordon EA, Wickman K, Velimirović B, Krapivinsky L, Clapham DE (March 1995). "The G-protein-gated atrial K+ channel IKACh is a heteromultimer of two inwardly rectifying K(+)-channel proteins". Nature. 374 (6518): 135–141. Bibcode:1995Natur.374..135K. doi:10.1038/374135a0. PMID 7877685. S2CID 4334467.
  95. ^ Corey S, Krapivinsky G, Krapivinsky L, Clapham DE (February 1998). "Number and stoichiometry of subunits in the native atrial G-protein-gated K+ channel, IKACh". The Journal of Biological Chemistry. 273 (9): 5271–5278. doi:10.1074/jbc.273.9.5271. PMID 9478984.
  96. ^ Kunkel MT, Peralta EG (November 1995). "Identification of domains conferring G protein regulation on inward rectifier potassium channels". Cell. 83 (3): 443–449. doi:10.1016/0092-8674(95)90122-1. PMID 8521474. S2CID 14720432.
  97. ^ Wickman K, Krapivinsky G, Corey S, Kennedy M, Nemec J, Medina I, Clapham DE (April 1999). "Structure, G protein activation, and functional relevance of the cardiac G protein-gated K+ channel, IKACh". Annals of the New York Academy of Sciences. 868 (1): 386–398. Bibcode:1999NYASA.868..386W. doi:10.1111/j.1749-6632.1999.tb11300.x. PMID 10414308. S2CID 25949938. Archived from the original on 2006-01-29.
  98. ^ Ball P (March 2008). "The crucible: Art inspired by science should be more than just a pretty picture". Chemistry World. 5 (3): 42–43. Retrieved 2009-01-12.
Quelle: http://en.wikipedia.org/wiki/Potassium_ion_channels