What triggers phosphorylation and dephosphorylation in Na-K ATPase pump?

• Phosphorylation is a widely used post-translational modification method of protein or enzyme activity.
• The sodium-potassium pump is an example of an active transport membrane protein/transmembrane ATPase.
• Using the energy from ATP, the sodium-potassium moves three sodium ions out of the cell and brings two potassium ions into the cell.

The above figure is the X-ray crystallography structure of the pump. And the yellow spots represent the amino acids that are phosphorylated and dephosphorylated during the process.

The above picture shows the amino acids of the pump phosphorylated and phosphorylated during the process.

STEPS OF WORKING OF Na+-K+ pump:

1. The sodium-potassium pump binds ATP and three intracellular Na+ ions.
2. ATP is hydrolyzed resulting in adenosine diphosphate (ADP) and inorganic phosphate. The free phosphate phosphorylates the sodium-potassium pump.
3. A conformational change in the pump exposes the Na+ ions to the outside. The phosphorylated form of the pump has a low affinity for Na+ ions, so they are released.
4. The pump binds two extracellular K+ ions. This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+ ions into the cell.
5. The unphosphorylated form of the pump has a higher affinity for Na+ ions than K+ ions, so the two bound K+ ions are released.
6. ATP binds, and the process starts again.

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