Sodium-calcium exchanger
| Sodium-calcium exchanger | ||
|---|---|---|
| Properties of human protein | ||
| Mass / length primary structure | 938 amino acids | |
| Secondary to quaternary structure | multipass membrane protein | |
| Isoforms | 4th | |
| Identifier | ||
| Gene name | SLC8A1 | |
| External IDs | ||
| Transporter classification | ||
| TCDB | 2.A.19.3.1 | |
| designation | Ca 2+ : cation antiporter | |
| Occurrence | ||
| Homology family | Na-Ca exchanger | |
| Parent taxon | multicellular animals | |
The sodium-calcium exchanger (engl. Often as a Na + / Ca 2+ exchanger, NCX , hereinafter) is a transmembrane protein into the cell membrane of animals which sodium - ions from the transporting one to the other side of the membrane and calcium ions in the opposite direction (hence " exchanger ").
Catalyzed transport
The transport equation:
Due to the opposite direction of transport of the two types of ions, the sodium-calcium exchanger is an example of an antiport .
The sodium-calcium exchanger transports sodium and calcium ions in a stoichiometric ratio of 3: 1, i.e. H. three sodium ions are exchanged for one calcium ion. Sodium ions are simply positively charged (Na + ), while calcium ions have two positive charges (Ca 2+ ). The sodium-calcium exchanger therefore exchanges three positive charges for two. As a result, there is a net charge transport through the membrane and the membrane potential changes. The transport through the sodium-calcium exchanger is therefore an electrogenic transport process.
The driving force for the sodium-calcium exchanger is the sodium gradient across the membrane. Sodium ions are transported from the side with the higher sodium concentration to the side of the lower. Calcium ions, on the other hand, are transported from the side with the lower calcium concentration to the side of the higher one. A transport of ions or other molecules against their concentration gradient is called active. As a rule, the intracellular sodium concentration is lower than the extracellular, and the same applies to the calcium concentration. Due to the high sodium gradient, the sodium-calcium exchanger transports sodium ions from the outside to the inside and calcium ions from the inside to the outside. The potential energy of the sodium gradient is used to transport calcium against its concentration gradient. Since the sodium gradient is the result of a primarily active transport process , namely the result of the activity of the sodium-potassium ATPase , the transport through the sodium-calcium exchanger represents a secondary active transport .
function
The sodium-calcium exchanger plays an important role in the calcium homeostasis of the cell. Due to the electrogenic nature of the transport, the cell is depolarized . If the intracellular sodium concentration rises sharply, the sodium-calcium exchanger works in the opposite direction (" reverse mode "), i. That is, it carries sodium ions out of the cell and lets calcium ions in. In this way, the sodium-calcium exchanger can not only contribute to calcium homeostasis, but also to calcium signaling of the cell.
The sodium-calcium exchanger is particularly important for the function of electrically excitable cells, i.e. H. Muscles (both skeletal , smooth muscle, and heart muscle ) and nerve cells .
literature
- Clark RB, Bouchard RA, Giles WR: Action potential duration modulates calcium influx, Na (+) - Ca2 + exchange, and intracellular calcium release in rat ventricular myocytes . In: Ann. NY Acad. Sci. . 779, April 1996, pp. 417-29. PMID 8659858 .
- Lytton J: Na + / Ca2 + exchangers: three mammalian gene families control Ca2 + transport . In: Biochem. J. . 406, No. 3, September 2007, pp. 365-82. doi : 10.1042 / BJ20070619 . PMID 17716241 .
Individual evidence
- ↑ a b TCDB: 2.A.19
- ↑ Jassal: Na + / Ca2 + exchanger transport. (No longer available online.) Reactome, June 5, 2009, formerly in the original ; accessed on September 4, 2010 (English). ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
