Conservation of a single insulin receptor binding site.
Each IR features two binding sites. Each one of them is formed by two components: binding site 1 is contained in the first three domains of one monomer, and comprises the conserved surface on L1 and the carboxy-terminal of the ID, which could not be crystallised in the IR ectodomain structure. In IGF-1, binding additionally involves the CR region. Binding site 2 is contained in the other monomer and it is thought to involve one or more of the FnIII domains. This figure shows the conservation of the (A) inner and (B) outer surfaces of a single binding site. It is evident that the inner surface is considerably more conserved, due in part to its role in dimer formation. The figure is based on the coordinates of PDB structure 2DTG and residue conservation is indicated in the same colour scale as in previous figures.