|Name:||potassium inwardly-rectifying channel, subfamily J, member 12|
|Old Name:||potassium inwardly-rectifying channel, subfamily J, inhibitor 1|
|PubMed (7859381):|| Wible BA, De Biasi M, Majumder K, Taglialatela M, Brown AM. Cloning and functional expression of an inwardly rectifying K+ channel fromhuman atrium.Circ Res. 1995 Mar;76(3):343-50. PMID: 7859381 [PubMed - indexed for MEDLINE]|
The cardiac inward rectifier current (IK1) contributes to the shape and duration of the cardiac action potential and helps to set the resting membrane potential. Although several inwardly rectifying K+ channels (IRKs) from different tissues have been cloned recently, the nature and number of K+ channels contributing to the cardiac IK1 are presently unknown. To address this issue in human heart, we have used the reverse-transcriptase-polymerase chain reaction (PCR) technique with human atrial total RNA as a template to identify two sequences expressed in heart that are homologous to previously cloned IRKs. One of the PCR products we obtained was virtually identical to IRK1 (cloned from a mouse macrophage cell line); the other, which we named hIRK, exhibited < 70% identity to IRK1. A full-length clone encoding hIRK was isolated from a human atrial cDNA library and functionally expressed in Xenopus oocytes. This channel, like IRK1, exhibited strong inward rectification and was blocked by divalent cations. However, hIRK differed from IRK1 at the single-channel level: hIRK had a single-channel conductance of 36 pS compared with 21 pS for IRK1. We have identified single channels of 41, 35, 21, and 9 pS in recordings from dispersed human atrial myocytes. However, none of these atrial inward rectifiers exhibited single-channel properties exactly like those of cloned hIRK expressed in oocytes. Our findings suggest that the cardiac IK1 in human atrial myocytes is composed of multiple inwardly rectifying channels distinguishable on the basis of single-channel conductance, each of which may be the product of a different gene.
|PubMed (12417321):|| Kaibara M, Ishihara K, Doi Y, Hayashi H, Ehara T, Taniyama K. Identification of human Kir2.2 (KCNJ12) gene encoding functional inwardrectifier potassium channel in both mammalian cells and Xenopus oocytes.FEBS Lett. 2002 Nov 6;531(2):250-4. PMID: 12417321 [PubMed - indexed for MEDLINE]|
Arginine residue at position 285 (R285) in the intracellular C-terminal domain of inward rectifier potassium channel Kir2.2 is conserved in many species, but missing in previously reported human Kir2.2 sequences. We here identified the human Kir2.2 gene in normal individuals, which contained R285 in the deduced amino-acid sequence (hKir2.2/R285). All 30 individuals we examined were homozygous for Kir2.2/R285 gene. The hKir2.2/R285 was electrophysiologically functional in both mammalian cells and Xenopus oocytes. However, the hKir2.2 missing R285 was functional only in Xenopus oocytes, but not in mammalian cells. Thus, R285 in Kir2.2 is important for its functional expression in mammalian cells.
>gnl|TC-DB|Q14500 1.A.2.1.9 ATP-sensitive inward rectifier potassium channel 12 MTAASRANPYSIVSSEEDGLHLVTMSGANGFGNGKVHTRRRCRNRFVKKNGQCNIEFANMDEKSQRYLADMFTTCVDIRW RYMLLIFSLAFLASWLLFGIIFWVIAVAHGDLEPAEGRGRTPCVMQVHGFMAAFLFSIETQTTIGYGLRCVTEECPVAVF MVVAQSIVGCIIDSFMIGAIMAKMARPKKRAQTLLFSHNAVVALRDGKLCLMWRVGNLRKSHIVEAHVRAQLIKPRVTEE GEYIPLDQIDIDVGFDKGLDRIFLVSPITILHEIDEASPLFGISRQDLETDDFEIVVILEGMVEATAMTTQARSSYLANE ILWGHRFEPVLFEEKNQYKIDYSHFHKTYEVPSTPRCSAKDLVENKFLLPSANSFCYENELAFLSRDEEDEADGDQDGRS RDGLSPQARHDFDRLQAGGGVLEQRPYRRESEI