Keeping It Simple : Kinetic Models for the Sodium Pump

The Post-Albers reaction scheme of the Na⁺,K⁺-ATPase has been remarkably successful, for over a quarter-century, in explaining the biochemical behavior of the isolated enzyme, and is still the backbone of current biophysical models for the various transport modes (electrogenic Na/K exchange; electroneutral and electrogenic Na/Na exchanges; K/K exchange, etc.) of the sodium pump. Because of its unique ability to accommodate such a vast array of observations, any shortcomings or ambiguities of the model are viewed with justified concern by some, or expediently ignored by others. An article by Suzuki and Post (1997) in this issue of The Journal of General Physiology brings a measure of clarity to some such problems and thus reaffirms the model's power and also makes a case for greater precision (or less ambiguity) in nomenclature when the model is extended beyond its original purview to include sidedness, occluded forms, and occupancy...