Figure 1

Insulin sequence and structure. (a) Primary sequence (top) of the A (blue) and B (grey) chains of human insulin, highlighting disulfide bonds (yellow), site 1-binding residues (underlined) and site 2-binding residues (bold)14. Ribbon diagram of insulin (2Zn-coordinated T6 conformation16 PDB entry 1MSO) showing the location of the three αhelices and the three disulfide bonds. (b) Schematic diagram of native cystine and isomeric cis- and transdicarba bridges.