Contact: Poul Nissen
Caption: The structure of the sodium-potassium pump is presented in a schematic cell membrane. The extracellular space is situated above and the intracellular space below the figure. The left-hand side of the figure shows the experimental reproduction of the pump's structure in the sodium-bound state. The reproduction is based on x-ray crystallography. The blue web shows how atoms are situated in long chains of amino acids which make up the protein molecule that constitutes the pump. The central section of the figure is a schematic presentation of the structure in which the different colors represent the various movable parts of the pump. The approximate position of the three Na+ ions is indicated with small, yellow balls. To the right, the structure of the potassium-bound state is shown using the same color codes and showing the two potassium ions as dark purple balls. The structural changes are evident. The structures correspond to two central steps in the pump's functional cycle, which pumps three sodium ions out of the cell for every two potassium ions pumped in.
Credit: Aarhus University
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