NaKPumpe

NaKPumpe, frequently referred to as the sodium-potassium pump, is a transmembrane enzyme that helps maintain the gradients of sodium and potassium ions across the plasma membrane in most animal cells. It uses energy from ATP hydrolysis to transport three Na+ ions out of the cell and two K+ ions into the cell per cycle. This activity underpins the resting membrane potential, cell volume regulation, and drives secondary active transport mechanisms.

The pump is a membrane protein composed mainly of alpha and beta subunits, with possible regulatory subunits in some tissues. It cycles between conformations known as E1 and E2. In the cytoplasm, three Na+ ions bind to the pump, which is then phosphorylated by ATP, triggering a conformational change that releases Na+ outside. Next, two extracellular K+ ions bind, the pump is dephosphorylated, and the protein returns to the original orientation, releasing K+ inside. This sequence couples ATP hydrolysis to ion transport and maintains the ion gradients that power many cellular processes.

In mammals, multiple isoforms of the alpha and beta subunits exist, with tissue-specific expression patterns that influence kinetics and regulatory properties. Hormonal signals, intracellular Na+ concentration, and phosphorylation states can modulate pump activity, adjusting cellular excitability and volume as needed.

Clinical relevance includes pharmacological inhibition by cardiac glycosides such as digitalis, which increases intracellular Na+ and alters Ca2+ handling to strengthen cardiac contraction in certain heart diseases. Genetic mutations in ATP1A2 or ATP1A3 are linked to neurological disorders including some epilepsies and migraines. Altered NaKPumpe function is also discussed in the context of hypertension and kidney function.