The Na+/K+ ATPase pump is a tetramer consisting of:
Purified sodium potassium ATPase from kidney outer medulla analyzed by SDS PAGE reveals catalytic alpha subunit about 112 kilodaltons with ten membrane spans and beta subunit about 55 kilodaltons glycosylated single pass plus small FXYD regulatory subunit 6 to 10 kilodaltons modulating kinetics. Early radiation inactivation, freeze fracture and crosslinking experiments indicated functional unit larger than heterodimer. Kinetic studies combined with electron microscopy suggested association of two heterodimers. High resolution structures show extracellular domain of beta contacting alpha of sam
Ref: Jorgensen et al., Biochim Biophys Acta, Na+/K+ ATPase Tetrameric Structure 2 Alpha 2 Beta Assembly.