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Kir5.1

potassium inwardly-rectifying channel, subfamily J, member 16
Synonyms: Kir5.1 kcnj16 BIR9. Symbol: Kcnj16

Introductions


Genes


Kcnj16 : potassium inwardly-rectifying channel, subfamily J, member 16

RGD ID Chromosome Position Species
61824 10 100514180-100515949 Rat
62115 11 110829347-110889282 Mouse
1343172 17 68071426-68131749 Human

Transcripts


Acc No Sequence Length Source
NM_053314 NCBI
NM_010604 NCBI
NM_018658 NCBI
NM_170741 NCBI
NM_170742 NCBI

Ontologies


Accession Name Definition Evidence
GO:0016021 integral to membrane Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane. IEA
GO:0016020 membrane Double layer of lipid molecules that encloses all cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. IEA

Interactions


The functional properties of heteromeric Kir4.1/Kir5.1 channels are profoundly different to their parental subunits; homomeric Kir4.1 channels are only mildly sensitive to intracellular pH (IC50 ∼ 6.0) and have a single channel conductance of approximately 10 pS. By contrast, heteromeric Kir4.1/Kir5.1 channels are highly sensitive to intracellular pH (IC50 ∼ 6.8) and have a single channel conductance of ∼45 pS with multiple short-lived, subconductance states (Pessia 1996 [1042], Pessia 2001 [1020], Konstas [1019], Rapedius [1043], Tanemoto [1013], Giwa [1024], Xu [1023]).

Proteins


Structures


Given the tetrameric nature of the K+ channel pore it is assumed that the central ion conduction pathway is not formed unless all four of the gating helices are in their ‘open’ conformation. Therefore, one structural model to explain the existence of K+ channel subconductance states is that these sublevels originate at the helix-bundle crossing due to successive movements of the four gating helices from the closed to open states, each movement producing a ‘partial’ opening of the channel on the way to the fully open state (Bezanilla [1044]). An alternative model proposed by Chapman & VanDongen suggests that the sublevels seen in the voltage-gated Kv2.1 channel originate from asymmetric conformations adopted by the selectivity filter in response to individual movements of the four gating helices (Chapman 2005 [1046]). Either way, both models assume that the allosteric interactions between identical subunits in a homomeric channel are highly cooperative, resulting in rapid transitions between the sublevels which are not resolved in the timescales of most single-channel recordings, making their analysis difficult, especially when obscured by noise and filtering. This behaviour, therefore, gives the appearance of a smooth and binary transition between the open and closed states (Bezanilla [1044], Chapman 2005 [1046]).

Distributions


Expressions


basolateral small conductance K+ channel in the distal nephron as well as pH-sensitive K+ channels in chemosensitive neurons (Pessia 1996 [1042], Pessia 2001 [1020]). Likewise, heteromeric Kir4.2/Kir5.1 channels have been reported in hepatic and pancreatic tissues (Pessia 2001 [1020], Pearson [205], Hill [1031]).

Functionals


Kinetics


Models


The simplest models of ion channel gating are binary and alternate between two discrete permeation states: open and closed. The movement between these two states is thought to be controlled by a ‘gate’ which physically impedes the flow of ions in the closed state but which moves out of the way during the open state. However, such simple models of channel gating are challenged by the observation of intermediate conductance, or ‘subconductance’ levels, such as those seen in heteromeric Kir4.0/Kir5.1 channels as well as many other types of ion channel (Bezanilla [1044], Fox [1045], Chapman 2005 [1046], Chapman 1997 [1047]).

References


[1037 : 21633011]
[1038 : 21239463]
[1039 : 20926613]
[1040 : 19665991]
[1041 : 14618155]
[1042 : 8670799]
[1019 : 12456399]
[1020 : 11306656]
[205 : 9882736]
[1031 : 11804844]
[1043 : 18690035]
[1013 : 10856114]
[1024 : 11598908]
[1022 : 10790154]
[1044 : 16043771]
[1045 : 2441065]
[1046 : 16043772]
[1047 : 9017198]

Credits