The sodium pump (Na + /K + -ATPase; sodium- and potas-sium-activated adenosine 5¢-triphosphatase; EC ) has been under investigation formore than fourdecades. During this time, the knowledge about the structure and properties of the enzyme has increased to suchan extent that specializedgroupshave formedwithin thisfield that focuson specific aspects of the active ion transport catalyzed by this enzyme.