Figure 1
From: Activation of signaling receptors: do ligands bind to receptor monomer, dimer, or both?
Dual model for receptor activation. Left panels illustrate a cytokine receptor; right panels illustrate a receptor tyrosine kinase like MET. Each receptor is composed of an extracellular domain (in red), a transmembrane helix (in lime green), and an intracellular domain (in steel blue and yellow for the inactive and active states, respectively). (A) Before binding the ligand (green), the receptor exists as both monomer and dimer. (B) The ligand binds to either monomeric or dimeric receptor. (C) Both binding routes lead to the same activated receptor complex.