Sequence Studies on Na,K-ATPase

Abstract

Na, K-ATPase is the enzyme responsible for the active transport of Na⁺ and K⁺ across cell membranes. Cardiac glycosides, such as digitalis and ouabain, specifically bind to and inhibit Na, K-ATPase, and it is thought that this enzyme is the pharmacological receptor for these drugs. For our sequence studies we have purified gm quantities of Na, K-ATPase from the outer medulla of lamb kidney. The highly purified enzyme is solubilized in 1% SDS, and chromatographed on a Sepharose CL-6B column run in 0.1% SDS. This procedure separates the three proteins present in the preparation: a (catalytic subunit, M_r ≃ 100,000), β (glycoprotein, M_r ≃ 50,000) and γ (proteolipid, M_r ≃ 12,000). The γ component is separated from salts, lipids and other low molecular weight material by chromatography on Sephadex LH-60 in an organic solvent.