Insulin receptor bound to insulin

3D Model

The insulin receptor is found in all tissues, it is a transmembrane receptor which has enzymatic activity as a tyrosine kinase. When insulin binds to the receptor, the intracellular part phosphorylates tyrosine residues on nearby proteins. Many growth factor receptors belong to this family and mutations in them are frequently oncogenic. The inactive receptor sits in an inhibited state with the kinase domains separated from each other and unable to function. When insulin binds it crosslinks the A (blue) and B (green) chains, causing a structural rearrangement like unfolding a deckchair. This creates the T shape receptor shown here with the kinase domains brought together and able to phosphorylate their substrates. Up to four insulin molecules can bind to one receptor, two shown in yellow are in what is called ‘site 1’ and two (identical but in purple rather than yellow for clarity) in ‘site 2’.