Intrinsically Disordered Peptide Nanofibers from A Structured Motif within Proteins

Intrinsically disordered regions (IDRs) are ubiquitous in pro-teins, orchestrating complex cellular signaling through high-er-order protein assemblies. However, the properties and functions of intrinsically disordered peptide (IDP) assemblies are largely underexplored. This work unveiled a facile strategy for engineering IDP assemblies. We demonstrate that conjugating a structured motif derived from a protein's phosphorylation site to a self-assembling tripeptide unexpectedly yields self-assembled nanofibers with intrinsic disorder. Specifically, by using glycine linker to attach a pentapeptide derived from a phosphorylation site within a random coil region of SRC kinase to the C-terminus of a widely used self-assembling enabler, we generated a phosphorylated octapeptide. The octapeptide exhibits cell compatibility and forms a hydrogel upon dephosphorylation. Cryo-electron microscopy structural analysis of the nanofibers reveals that the peptides adopt two types of helical arrangements, but exhibit intrinsic disorder at the periphery of the nanofibers. The hydrogels exhibit decreased protein adsorption with increasing peptide concentration. This study represents the first instance of a structured random coil within a protein transitioning into an intrinsically disordered state within self-assembled peptide nanofibers, expanding the pool of peptide sequences for IDPs and providing valuable insights for engineering of peptide nanofibers with intrinsic disorder for the development of cell compatible biomaterials.