GIRK4 This potassium channel is controlled by G proteins. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages. The inward rectification is mainly due to the blockage of outward current by internal magnesium. Can be blocked by external barium. Defects in KCNJ5 are the cause of long QT syndrome type 13 (LQT13). It is a heart disorder characterized by a prolonged QT interval on the ECG and polymorphic ventricular arrhythmias. They cause syncope and sudden death in response to excercise or emotional stress, and can present with a sentinel event of sudden cardiac death in infancy. Defects in KCNJ5 are the cause of familial hyperaldosteronism type 3 (FH3). A form of hyperaldosteronism characterized by hypertension secondary to massive adrenal mineralocorticoid production. Like patients with familial hyperaldosteronism type 1 (glucocorticoid-remediable aldosteronism), patients with FH3 present with childhood hypertension, elevated aldosteronism levels, and high levels of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol. However, hypertension and aldosteronism are not reversed by administration of exogenous glucocorticoids and patients require adrenalectomy to control hypertension. Somatic mutations in KCNJ5 have been found in aldosterone-producing adrenal adenomas and can be responsible for aldosteronism associated with cell autonomous proliferation. These are typically solitary, well circumscribed tumors diagnosed between ages 30 and 70. They come to medical attention due to new or worsening hypertension, often with hypokalemia. KCNJ5 mutations produce increased sodium conductance and cell depolarization, which in adrenal glomerulosa cells produces calcium entry, the signal for aldosterone production and cell proliferation. Belongs to the inward rectifier-type potassium channel (TC 1.A.2.1) family. KCNJ5 subfamily. Note: This description may include information from UniProtKB.
Protein type: Channel, potassium; Membrane protein, integral; Membrane protein, multi-pass
Chromosomal Location of Human Ortholog: 11q24.3
Cellular Component:  external side of plasma membrane; plasma membrane; T-tubule; voltage-gated potassium channel complex
Molecular Function:  G-protein activated inward rectifier potassium channel activity; protein binding; voltage-gated potassium channel activity involved in atrial cardiac muscle cell action potential repolarization; voltage-gated potassium channel activity involved in ventricular cardiac muscle cell action potential repolarization
Biological Process:  membrane repolarization during atrial cardiac muscle cell action potential; membrane repolarization during ventricular cardiac muscle cell action potential; potassium ion import across plasma membrane; potassium ion transport; regulation of heart rate by cardiac conduction; regulation of ion transmembrane transport; ventricular cardiac muscle cell membrane repolarization
Disease: Hyperaldosteronism, Familial, Type Iii; Long Qt Syndrome 13
Reference #:  P48544 (UniProtKB)
Alt. Names/Synonyms: cardiac ATP-sensitive potassium channel; Cardiac inward rectifier; CIR; G protein-activated inward rectifier potassium channel 4; G protein-activated inward rectifier potassium channel 4 (GIRK4) (Potassium channel, inwardly rectifying, subfamily J, member 5) (Inward rectifier K+ channel Kir3.4) (Heart KATP channel) (KATP-1) (Cardiac inward rectifier) (CIR)...; GIRK-4; GIRK4; Heart KATP channel; Inward rectifier K(+) channel Kir3.4; inward rectifier K+ channel KIR3.4; IRK-4; IRK5; KATP-1; KATP1; KCNJ5; KIR3.4; Potassium channel, inwardly rectifying subfamily J member 5; potassium inwardly-rectifying channel J5; potassium inwardly-rectifying channel, subfamily J, member 5
Gene Symbols: KCNJ5
Molecular weight: 47,668 Da
Basal Isoelectric point: 5.24  Predict pI for various phosphorylation states
Select Structure to View Below


Protein Structure Not Found.

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