ROMK
| ATP-sensitive inward-rectifying potassium channel | ||
|---|---|---|
|
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| Cytoplasmic domain of an inward rectifying potassium channel of the mouse according to PDB 1N9P | ||
| Properties of human protein | ||
| Mass / length primary structure | 391 amino acids; 44.8 kDa | |
| Secondary to quaternary structure | multipass membrane protein | |
| Isoforms | ROM-K1, ROM-K2, ROM-K3 | |
| Identifier | ||
| Gene name | KCNJ1 | |
| External IDs | ||
| Transporter classification | ||
| TCDB | 1.A.2.1.1 | |
| designation | Inward rectifying potassium channels | |
| Occurrence | ||
| Parent taxon | Creature | |
| Orthologue | ||
| human | mouse | |
| Entrez | 3758 | 56379 |
| Ensemble | ENSG00000151704 | ENSMUSG00000041248 |
| UniProt | P48048 | O88335 |
| Refseq (mRNA) | NM_000220 | NM_019659 |
| Refseq (protein) | NP_000211 | NP_062633 |
| Gene locus | Chr 11: 128.21 - 128.22 Mb | Chr 9: 32.2 - 32.21 Mb |
| PubMed search | 3758 |
56379
|
ROMK is the abbreviation for " R enal O uter M edullary Potassium ( K ) channel " (English = potassium channel of the outer renal medulla '), an ion channel , which play an important role in the elimination of the kidney potassium exerts. ROMK is the gene KIR1.1 (KCNJ1) encoding . Pathological mutations in this gene lead to severe congenital disorders of the potassium balance. Corresponding diseases affect the kidney tubules (tubules), which together with the glomeruli form the nephron , the smallest functional subunit of the kidney. With such tubulopathies there is no renal failure .
Expression of ROMK in the kidney
In the tubules ROMK is at two different sections expressed and exerts different functions from there.
In the thick ascending part (thigh) of Henle's loop , sodium and potassium are first transported from the primary urine via the Na-K-2Cl cotransporter via the lumen-side ( apical ) cell membrane into the tubular cell. While sodium and chloride are transported from the tubular cell via the lumen-distant ( basolateral ) cell membrane into the blood (reabsorption), the potassium returns to the primary urine via ROMK in the apical membrane and is there again for the transport of sodium and chloride into the Cell available. ROMK is to a certain extent responsible for the recycling of potassium in the Henle Loop . On the one hand, this recycling favors the reabsorption of common salt from the primary urine into the blood. On the other hand, potassium recycling via ROMK leads to an increase in the positive charge in the primary urine, and this in turn promotes the transport of calcium and magnesium from the primary urine into the blood.
In the collecting tube, ROMK is also expressed in the apical membrane of the collecting tube cell, but there it is responsible for the secretion of potassium from the blood into the urine. In the collecting tube, the majority of the excess potassium supplied with food is excreted into the urine via ROMK. If the potassium uptake with food increases, the density of ROMK in the collecting tube of the kidney increases. This is interpreted as an adaptation to the way of life of our Paleolithic ancestors who ate a diet high in potassium and low in table salt.
Medical importance
The loss of function of ROMK due to a mutation leads to Bartter syndrome type II . Immediately after birth, the affected children have too high a potassium level in the blood ( hyperkalemia ), which is attributed to a reduced excretion of potassium in the collecting tube of the kidneys. As the disease progresses, the potassium level in the blood drops, leading to hypokalemia . This is explained by the fact that the recycling of potassium via ROMK fails in the Henle Loop, which in turn hinders the reabsorption of table salt, calcium and magnesium from the primary urine into the blood. The sodium concentration in the primary urine increases, the urine flow in the collecting tube increases. This leads to a second potassium channel, the maxi-potassium channel, being activated in the collecting tube cells, which is closed with normal flow and normal salt concentration. This ultimately leads to a loss of potassium via the kidneys and a drop in the potassium concentration in the blood.
The time course of the disease with an increased potassium level immediately after birth and a decrease in potassium in the further course of the disease is explained by the fact that ROMK is expressed earlier than Maxi-K + in the development of the kidneys . The consequences of the disease are severe salt and potassium losses through the kidneys, which can lead to the breakdown of muscle cells ( rhabdomyolysis ) and periodic symptoms of paralysis ( periodic paralysis ), as well as growth disorders and disorders of mental development.
literature
- Ulrich Kerl: Characterization of interacting proteins of the renal ATP-dependent potassium channel ROMK. (Dissertation, University of Würzburg, Medical Faculty, 2005, doctoral thesis at Dokserv ).
swell
- ↑ Wen-Hui Wang: Regulation of ROMK (Kir1.1) channels: new mechanisms and aspects . In: American Journal of Physiology-Renal Physiology . tape 290 , no. 1 , December 9, 2005, p. F14-F19 , doi : 10.1152 / ajprenal.00093.2005 .
- ↑ MA Bailey, A. Cantone, Q. Yan, GG MacGregor, Q. Leng, JBO Amorim, T. Wang, SC Hebert, G. Giebisch, G. Malnic: Maxi-K channels contribute to urinary potassium excretion in the ROMK- deficient mouse model of Type II Bartter's syndrome and in adaptation to a high-K diet . In: Kidney International . tape 70 , no. 1 , April 17, 2006, p. 51-59 .