on-transporting ATPases, or "ion pumps," couple ATP hydrolysis to active ion translocation across membranes, a function essential for cell viability. Although much is understood about ion pumps, details of their transport mechanisms are unknown. Of utmost importance is delineating the three-dimensional structure at high resolution, which would allow integration of the biochemical and kinetic information. We focus on elucidating the three-dimensional structure of Na,K-ATPase, the Na+,K+ pump in the plasma membrane of all animal cells, using electron microscopy of two-dimensional crystals and image reconstruction from the recorded micrographs, complemented with relevant biochemical investigations.

We obtained the three-dimensional structure of Na,K-ATPase at 2.5-nm resolution and mapped the locations of its two subunits. Moreover, results from the combined structural and biochemical studies have implications for the oligomeric form of the functional unit and how ion transport might occur. Based on these findings, we proposed a model for the form and mechanism of the Na+,K+ pump.

Our continuing goals are to extend the structural resolution to 1.0 nm, which would allow identifying structures such as helices and channels, and pursue structural studies on H,K-ATPase, the stomach acid pump.