A reconstituted Na++K+ pump in liposomes containing purified (Na++K+-ATPase from kidney medulla

Liposomes containing either purified or microsomal (Na⁺,K⁺)-ATPase preparations from lamb kidney medulla catalyzed ATP-dependent transport of Na⁺ and K⁺ with a ratio of approximately 3Na⁺ to 2K⁺, which was inhibited by ouabain. Similar results were obtained with liposomes containing a partially purified (Na⁺,K⁺-ATPase from cardiac muscle. This contrasts with an earlier report by Goldin and Tong (J. Biol. Chem. 249, 5907–5915, 1974), in which liposomes containing purified dog kidney (Na⁺,K⁺)-ATPase did not transport K⁺ but catalyzed ATP-dependent symport of Na⁺ and Cl^?. When purified by our procedure, dog kidney (Na⁺,K⁺)-ATPase showed some ability to transport K⁺ but the ratio of Na⁺ : K⁺ was 5 : 1.