The ion transporter (EC 18.104.22.168, not a sodium channel) that maintains the electrochemical gradients of Na+ and K+ ions across the plasma membrane. It has two subunits, a catalytic α subunit (multiple isoforms; ATP1A4 is 1029 aa) that has the catalytic activity and a smaller β subunit of uncertain function. For each ATP hydrolysed it moves three sodium ions out of the cell, and two potassium ions in. The sodium gradient is used to drive various cotransport systems (see facilitated diffusion) and is essential for the action potential in excitable cells. The potassium gradient dissipates through the potassium leak channel and is the main basis for the normal resting potential. The α2 isoform in neural and muscle tissues is mutated in familial hemiplegic migraine-2.
Subjects: Medicine and Health — Chemistry.