Structural details of the insulin molecule.

(A) The structure of the insulin (PDB ID: 2G4M). A-Chain (orange); B-chain N-terminal (residues F1–G8) (red), B-chain α-helix (residues S9–C19) (black), B-chain C-terminal (residues G20–T30) (blue). The colored spheres represent the Cα atoms of the first and last residues of the A and B-chains. (B) The new ribbon representation shows the hydrophobic core of insulin, comprising the residues F24, L15, Y26, L11, V12, G8 (side chains shown in cyan), I2A and V3A (side chains shown in green). The hydroxyl group of Y26 and the oxygen atom of G8 are shown in red, and the disulfide bridges in yellow. (C) The hydrogen bonds between the residues neighboring Y24 and the A chain residues, G23(O)–N2A(N) and F25(N)–Y19A(O), are illustrated in blue dashed lines. Oxygen and nitrogen atoms are represented in red and blue, respectively.