How does a hydrocarbon staple affect peptide hydrophobicity?

Water is essential for the proper folding of proteins and the assembly of protein-protein/ligand complexes. How water regulates complex formation depends on the chemical and topological details of the interface. The dynamics of water in the interdomain region between an E3 ubiquitin ligase (MDM2) and three different peptides derived from the tumor suppressor protein p53 are studied using molecular dynamics. The peptides show bimodal distributions of interdomain water densities across a range of distances. The addition of a hydrocarbon chain to rigidify the peptides (in a process known as stapling) results in an increase in average hydrophobicity of the peptide-protein interface. Additionally, the hydrophobic staple shields a network of water molecules, kinetically stabilizing a water chain hydrogen-bonded between the peptide and MDM2. These properties could result in a decrease in the energy barrier associated with dehydrating the peptide-protein interface, thereby regulating the kinetics of peptide binding.