Figure 2

Activation of insulin receptor. The insulin receptor consists of 2 extracellular a subunits that bind insulin and 2 transmembrane β subunits with tyrosine kinase activity. Insulin binding to the a subunit induces the transphosphorylation of one β subunit by another on specific tyrosine residues in an activation loop, resulting in the increased catalytic activity of the kinase. The receptor also undergoes autophosphorylation at other tyrosine residues in the juxtamembrane regions and intracellular tail The activated IR then phosphorylates tyrosine residues on intracellular substrates.