Sodium and potassium-exchanging adenosine triphosphatase (Na,K-ATPase) in the kidney is associated with the subunit ( , FXYD2), a single-span membrane protein that modulates ATPase properties. Rat and human occur in two splice variants, a and b, with different N termini. Here we investigated their structural heterogeneity and functional effects on Na,K-ATPase properties. Both forms were post-tr...