Sodium-calcium exchanger

Of the sodium -calcium exchanger (English often exchanger as Na / Ca2 NCX, hereinafter) is a transmembrane protein into the cell membranes of animals, which transports sodium ions from one side to the other side of the membrane and calcium ions in the opposite direction (hence " exchanger ").

The catalyzed transport

The transport equation:

Due to the opposite direction of transport of the two types of ions of the sodium -calcium exchanger is an example of an anti port. Of the sodium -calcium exchanger is transported sodium and calcium ions in a stoichiometric ratio of 3:1, i.e., three sodium ions replaced by a calcium ion. Sodium ions are easily positively charged ( Na ), while the calcium ions have two positive charges (Ca2 ). Thus, the sodium -calcium exchanger exchanges three positive charges against two. As a result therefore there is a net charge of transportation 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 of higher sodium concentration on the side of the lower one. Calcium ions, however, are conveyed from the lower side of the calcium concentration on the side of higher. A transport of ions or other molecules against their concentration gradient is called active. In general, the intracellular sodium concentration is lower than the extracellular, with the calcium concentration it behaves exactly like that. Due to the high sodium gradient of sodium -calcium exchanger sodium ions transported 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 towards its concentration gradient. Since the sodium gradient is a result of a primary active transport process, namely result of the activity of sodium-potassium ATPase, the transport through the sodium -calcium exchanger represents a secondary active transport

Function

Of the sodium -calcium exchanger is important for calcium homeostasis of the cell. Due to the electrogenic nature of the transport, the cell is depolarized it. With a strong increase of the intracellular sodium concentration of the sodium -calcium exchanger is working in the opposite direction ( "reverse mode" ), i.e., he transported sodium ions out of the cell and can be of calcium ions into it. In this way, the sodium -calcium exchanger can not only contribute to calcium homeostasis, but also to calcium signaling the cell. Of the sodium -calcium exchanger is important for the function of electrically excitable cells, i.e., muscle (both skeletal muscle, smooth muscle and the heart muscle) and neural cells.

Protein isoform Human Genome Organisation Depolarization Smooth muscle tissue Digital Object Identifier
594943
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