Protein of the Year!

Okay, I’ll keep this short.

The sodium potassium pump is more important than we realize. It is involved in a wide range of cellular and physiological functions. Here's a quick list of just a few things:

1. Insulin secretion from the pancreas
2. Neuron action potentials (70% of ATP in neurons is for my protein)
3. Heart contraction
4. Import of glucose and amino acids (via facilitated transport)
5. Absorption of water by the kidneys

Bound Potassium Ions

Depending on cell type, there are between 800,000 and 30 million pumps on the surface of cells (1). The sodium potassium pump (Na⁺/K⁺ ATPase) exports 3 Na⁺ ions and then imports 2 K⁺ ion and this ability is very important for establishing an electrochemical gradient across the cell membrane. This gradient is part of most cellular functions dealing with the transport of small molecules or ions across the cell membrane. The electrochemical gradient is so central that 25% of the total energy consumption of a resting human is used for this end. This protein is also a drug target for people with congestive heart failure because by inhibiting this pump, ion concentrations are disrupted and results in more forceful heart contractions. While just about every protein is important for an organism’s survival, few are involved in as many different essential functions as the sodium potassium pump.

 
The sodium potassium pump is also structurally impressive. It is a relatively large protein which spans the cell membrane. The central alpha helices form a tunnel (purple) for sodium and potassium ions and can selectively bind Na⁺ or K⁺ depending upon its state (phosphorylated or dephosphorylated). The army green region is where the ATPase function is located. The yellow spheres represent phosporylation. The discovery of this protein resulted in a Nobel Prize in 1997. Thus, it goes without saying, this protein deserves to be in the protein hall of fame.



For a brief function summary, see the figures below.

Overview of ion pumping cycle

Gradient Quantified

And let's wrap up with some quick pictures.

 

Ouabain - an inhibitor is bound

1. http://www.vivo.colostate.edu/hbooks/molecules/sodium_pump.html