This is the non-catalytic component of the active enzyme, which catalyzes the hydrolysis of ATP coupled with the exchange of Na(+) and K(+) ions across the plasma membrane. The exact function of the beta-3 subunit is not known. The sodium/potassium-transporting ATPase is composed of a catalytic alpha subunit, an auxiliary non-catalytic beta subunit and an additional regulatory subunit. Nervous system specific. During embryogenesis rapid accumulation of beta 3 mRNA begins at stage 14 (early neurula). Belongs to the X(+)/potassium ATPases subunit beta family.