Does the Sodium Pump have Secret Levels?

Abstract

Animal life without sodium pumps, or to be more precise, without the Na,K-ATPase, is not possible. Animal cells need to maintain a high K+ and a low Na+ concentration in their cytoplasm as opposed to high Na+ and low K+ concentrations of their extracellular environment. The Na,K-ATPase creates electrochemical potential gradients for both ion species that are essential for cellular functions such as secondary active transport, excitability, and volume regulation. In 1957 the Na,K-ATPase was discovered by J. C. Skou (1), and since then there has been a wealth of studies published, providing increasing knowledge and insight into the structure and function of this active ion transporter of the plasma membrane at many different levels. Quite early the pump cycle was elucidated, the stoichiometry of 3 Na+/2 K+/1 ATP established, a consecutive or Ping-Pong-type mechanism (first Na+ out then K+ in) was demonstrated, and all these results were compiled into the famous Post-Albers cycle (2) that became the prototype of the reaction scheme for all P-type ATPases.