The role of carboxyl groups of Na+/K+-ATPase in the interaction with divalent cations.

Mg2+-induced subconformational changes of the E1 conformation of partly purified pig kidney Na+/K+-ATPase were studied by fluorescence techniques. In the enzyme with carboxyl groups modified by carbodiimide in the presence of an exogenous nucleophile the efficiency to pass through conformational substates was substantially lower than in the unmodified enzyme. Magnesium could form bridges between carboxyl groups near the membrane/water interface and negatively charged phospholipid polar heads.