Fig. 2
From: The design and development of covalent protein-protein interaction inhibitors for cancer treatment
The crystal structure of three different classes of PPIs. a Linear sequences comprise primary peptide epitopes (e.g., LM of DNA polymerase III bound to the binding pocket of the SC (PDB: 3D1F)). b The secondary structure of epitopes binds as a single unit, e.g., an α-helix (NusB-NusE PPI (PDB: 3R2C)). c In tertiary structural epitopes, the binding interface is not continuous and both sides of PPI interface are needed (e.g., IL-2/IL-2Ra PPI (PDB 1Z92))