Molecular Genetics of Na,K-ATPase

This chapter discusses the molecular genetics of Na,K-ATPase. The Na,K-ATPase is an integral membrane enzyme found in all cells of higher organisms and is responsible for the ATP-dependent transport of Na+ and K+ across the cell membrane. The ion gradients formed by this enzyme are essential for the Na+-coupled transport of various nutrients, including glucose and amino acids, into cells movement of such ions as Ca2+ and H+ across the membrane, and osmotic balance and cell-volume regulation. Protein synthesis and receptor-mediated endocytosis and recycling also depend on the resulting ion gradients. Because two K+ ions are pumped into the cell for every three Na+ ions expelled, an electrochemical gradient is established. In many instances, the information is more easily obtained using recombinant DNA techniques, and in some cases it can be obtained by no other means. The power of this approach has clearly been demonstrated by recent advances in understanding Na, K-ATPase. Na, K-ATPase also appears to play a role in determining the nutrient and ion composition of the cerebrospinal fluid and aqueous humor. In addition, the enzyme is responsible for fluid movement across transport epithelia in the gastrointestinal tract, the nasotracheal lining, and the kidney. Fluid reabsorption from the lung at birth also may depend in part on functioning of the Na, K-ATPase.