the polarized distribution of nakatpase role of the interaction between beta subunits the very existence of higher metazoans depends on the vectorial transport of substances across epithelia a crucial element of this transport is the membrane enzyme nakatpase not only is this enzyme distributed in a polarized manner in a restricted domain of the plasma membrane but also it creates the ionic gradients that drive the net movement of glucose amino acids and ions across the entire epithelium in a previous work we have shown that nakatpase polarity depends on interactions between the beta subunits of nakatpases located on neighboring cells and that these interactions anchor the entire enzyme at the borders of the intercellular space in the present study we used fluorescence resonance energy transfer and coprecipitation methods to demonstrate that these beta subunits have sufficient proximity and affinity to permit a direct interaction without requiring any additional extracellular molecules to span the distance