Talk:Potassium channel

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Untitled

Blocking agents for potassium channels also are: Cs+,H+,Ba++,Rb+,Sr++,Mg++,Na+,Capsaicin, Noxiustoxin, Chlotrimazol, Spermine, Spermidine

Kir-channels can shut down secretion of growth hormone or prolactin from the anterior pituitary (see Bertil Hille: ion channels of excitable membrane) —Preceding unsigned comment added by 141.5.4.128 (talk) 11:54, 24 April 2008 (UTC)[reply]

"Potassium channels are found in most cells, and control the electrical excitability of the cell membrane." Strictly speaking, K+ channels are also expressed in non-excitable cells, such as red blood cells, epithelial cells, endothelial cells, etc. I'm taking the liberty of changing this statement. I also re-organized the page a little, added references to cardiac and pancreatic tissue and added another reference.

These K+ channels are incorrect. Please review recent papers by Roderick MacKinnon, for which he received a Nobel prize for correctly photographing (through x-ray crystallography) a channel and discovering how they truly function, it is much less graceful and elaborate as that which is on this page. (from anon, jan 24)

Thank you for your suggestion! When you feel an article needs improvement, please feel free to make those changes. Wikipedia is a wiki, so anyone can edit almost any article by simply following the Edit this page link at the top. You don't even need to log in (although there are many reasons why you might want to). The Wikipedia community encourages you to be bold in updating pages. Don't worry too much about making honest mistakes — they're likely to be found and corrected quickly. If you're not sure how editing works, check out how to edit a page, or use the sandbox to try out your editing skills. New contributors are always welcome. --Arcadian 03:46, 25 January 2007 (UTC)[reply]

Types table

There seems to be some mistake in the table of potassium channel in the row on inwardly rectifying channels. It doesn't compare to the actual article on inwardly rectifying potassium channels. Reading this, you get the feeling that there is only G-protein-activated and ATP-sensitive kirs. That's not what Inward-rectifier potassium ion channel says. I'm not enough of an expert to know which one is right though. Does anybody know? --LasseFolkersen (talk) 09:09, 7 March 2008 (UTC)[reply]

The article is correct and the table is misleading. The table only lists Kir3 (G-protein regulated) and Kir6 (ATP regulated) while leaving out Kir1/2/4/5. I'll try and alter the table if I get a chance. --Dpryan (talk) 19:41, 7 March 2008 (UTC)[reply]

Thanks for the explanation. I have modified the table to add ROMK, but I think there may be too many subtypes to list in one table. In addition, the current table is somewhat focused on pharmacology (i.e., blocker and activators) and many potassium channels have no known pharmacology. Hence may I suggest that we simply point out that this table is not exhaustive and refer the reader to the respective potassium channel class pages for a complete list of class members? I have edited the article to try to make this clear. Cheers. Boghog2 (talk) 12:38, 9 March 2008 (UTC)[reply]

The statement (in the section on "Structure") "since sodium ions have greater charge density, they have a larger shell of water molecules surrounding them and thus are more bulky" is technically correct, but it is NOT the correct explanation of why potassium channels are impermeable to sodium. But the next section, "selectivity filter", gives the correct explanation. I suggest deleting this largely irrelevant, and misleading, sentence.24.47.61.206 (talk) 03:20, 25 November 2009 (UTC)[reply]

Done --Dpryan (talk) 06:02, 25 November 2009 (UTC)[reply]

Nest versus P-loop

There appears to be a conflict in some recent edits over a description of the selectivity filter structure between myself and JamesMilnerWhite (and an IP editor). The description of the region with the selectivity filter has been redefined as a nest (protein structural motif) while previous convention was to call it the P-loop.^[1]^[2]^[3]^[4]

I disagree with these edits on based on:

The term P-loop is commonly within the field^[1]^[2]^[3]^[4]
P-loop adds precision as it describes the loop between the pore helix and TM2/6 which forms the Pore
The referenced nest article, as current written, does not appear to apply as it describes anion binding.
The argument that P-loop is specific to Walker motifs is to presume that the term is exclusive to ATPases.

An inclusion of nest in the description of the structure is certainly fair. However, excising the P-loop description is in contradiction to convention within the K-channel field. I propose something like this as a compromise:

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 an isoleucine residue in eukaryotic potassium ion channel is often substituted with a valine residue in prokaryotic channels. This sequence adopts a unique main chain structure, structurally analogous to a nest protein structural motif.

Dbsseven (talk) 18:01, 8 June 2017 (UTC)[reply]

References

^ ^a ^b Choe S (February 2002). "Potassium channel structures". Nature Reviews. Neuroscience. 3 (2): 115–21. doi:10.1038/nrn727. PMID 11836519.
^ ^a ^b Proks P, Capener CE, Jones P, Ashcroft FM (October 2001). "Mutations within the P-loop of Kir6.2 modulate the intraburst kinetics of the ATP-sensitive potassium channel". The Journal of General Physiology. 118 (4): 341–53. PMID 11585848.
^ ^a ^b Kubisch C, Schroeder BC, Friedrich T, Lütjohann B, El-Amraoui A, Marlin S, Petit C, Jentsch TJ (February 1999). "KCNQ4, a novel potassium channel expressed in sensory outer hair cells, is mutated in dominant deafness". Cell. 96 (3): 437–46. PMID 10025409.
^ ^a ^b Capener CE, Shrivastava IH, Ranatunga KM, Forrest LR, Smith GR, Sansom MS (June 2000). "Homology modeling and molecular dynamics simulation studies of an inward rectifier potassium channel". Biophysical Journal. 78 (6): 2929–42. doi:10.1016/S0006-3495(00)76833-0. PMID 10827973.

I'm very familiar with the source material in this field, and I've examined the edits very closely. I agree with you about the literature typically calling it a P-loop, and that it is more accurate to describe it as "structurally analogous to" instead of actually being a nest motif. I support the version that you propose here. If a reliable source can be presented that states explicitly that K⁺ channels have a nest structure that should no longer described as a P-loop, I'll change my mind, but otherwise the statement about nest requires a "citation needed" tag. --Tryptofish (talk) 22:16, 8 June 2017 (UTC)[reply]

Thank you Tryptofish. I have given it a few days for JamesMilnerWhite to chime in and am now going to change the language. Dbsseven (talk) 13:45, 12 June 2017 (UTC)[reply]

I see JamesMilnerWhite has revised the edits. I am not entirely sure about the new language as it contradicts the anion binding nature of the nest description. Also there is no citation for using a nest description.Dbsseven (talk) 18:06, 15 June 2017 (UTC)[reply]

Muscarinic potassium channel

Hi all, The section on "Muscarinic potassium channel" seems out of place here. For such a general article, a brief but highly specific section on one particular channel subfamily seems out of place. (By analogy, all sorts of other highly medically relevant/interesting channels could have their own subsection here. The BK channel, various Kv-channels...) The content is already available through the GIRK link in the "Types" section.

I would propose removing this section. But since this is a reasonably substantial deletion, I thought worth discussing here. Dbsseven (talk) 18:35, 9 March 2018 (UTC)[reply]

Completely agree. Please go ahead and remove it. Boghog (talk) 20:09, 9 March 2018 (UTC)[reply]

I agree that it should not be a level-2 section, and should not focus specifically on muscarinics. It might be appropriate, however, to rewrite it as a subsection of the Regulation section, called Receptor modulation, and dealing with GIRKs more broadly. That's really a very important topic within the K⁺ channel field. --Tryptofish (talk) 23:20, 9 March 2018 (UTC)[reply]

Tryptofish I like the idea. Though in keeping with the broad nature of this article I imagine this should be written as generally as possible. Possibly also briefly covering Voltage-gated potassium channels and Calcium-activated potassium channels. With these level-3 sections we can cover voltage, ligand, and G-protein regulation of channel activity. Dbsseven (talk) 00:05, 10 March 2018 (UTC)[reply]

Potassium channel in fine art

Does this section really meet the inclusion criteria? I'm not really familiar with them which is why I'm not editing it but it really does not feel at all relevant... Anditres (talk) 06:53, 8 February 2022 (UTC)[reply]

[1a-1] Choe S (February 2002). "Potassium channel structures". Nature Reviews. Neuroscience. 3 (2): 115–21. doi:10.1038/nrn727. PMID 11836519.

[2a-2] Proks P, Capener CE, Jones P, Ashcroft FM (October 2001). "Mutations within the P-loop of Kir6.2 modulate the intraburst kinetics of the ATP-sensitive potassium channel". The Journal of General Physiology. 118 (4): 341–53. PMID 11585848.

[3a-3] Kubisch C, Schroeder BC, Friedrich T, Lütjohann B, El-Amraoui A, Marlin S, Petit C, Jentsch TJ (February 1999). "KCNQ4, a novel potassium channel expressed in sensory outer hair cells, is mutated in dominant deafness". Cell. 96 (3): 437–46. PMID 10025409.

[4a-4] Capener CE, Shrivastava IH, Ranatunga KM, Forrest LR, Smith GR, Sansom MS (June 2000). "Homology modeling and molecular dynamics simulation studies of an inward rectifier potassium channel". Biophysical Journal. 78 (6): 2929–42. doi:10.1016/S0006-3495(00)76833-0. PMID 10827973.

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