5 Beta,14 beta-androstane-3 beta,14-diol binds to the digitalis receptor site on Na/K-ATPase.

5 beta,14 beta-Androstane-3 beta,-14-diol, the lead (minimum) structure in digitalis compounds, shows the same characteristics of interaction with Na/K-ATPase as ordinary digitalis compounds judged by the following six criteria: (I) shape of the concentration-inhibition curves, (II) species differences in affinity for the enzyme, (III) apparent competition with K+, (IV) competition with digitoxigenin for binding to the enzyme, (V) stabilization of phosphoenzyme formed from ATP, and (VI) enhancement of phosphorylation from orthophosphate.