Sodium-Potassium Pump, Sodium-Bound State (image) Aarhus University Caption The figure shows the tunnel-like entry point to the binding sites of the sodium-potassium pump in the sodium-bound state. The three small sodium ions are bound inside the pump (violet spheres to the left), whereas there is not sufficient room for the larger potassium ions (green spheres to the right). The blue web shows the inner surface of the protein blocking the potassium ions. The letter code indicates the amino acids shown in the pump, which are essential to the binding process. Credit Bente Vilsen and Flemming Cornelius Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.