Hierarchical assembly of intrinsically disordered short peptides

The understanding of how short peptide assemblies transit from disorder to order remains limited due to the lack of atomistic structures. Here, we report the cryo-EM structure of the nanofibers short intrinsically disordered peptides (IDPs). On lowering pH or adding calcium ions, the IDP transitions from individual nanoparticles to nanofibers containing an aromatic core and a disordered periphery were composed of 2–5 amino acids. Protonating the phosphate or adding more metal ions further assembles the nanofibers into filament bundles. The assemblies of the IDP analogs with controlled chemistry, such as phosphorylation site, hydrophobic interactions, and sequences, indicate that metal ions interact with the flexible periphery of the nanoparticles of the IDPs to form fibrils and enhance the interfibrillar interactions to form filament bundles. Illustrating that an IDP self-assembles from disorder to order, this work offers atomistic molecular insights to understand assemblies of short peptides driven by noncovalent interactions. [Display omitted] •Hydrophobic interactions drive IDPs to self-assemble to form assemblies•Cryo-EM reveals the atomic structures of fibrillar assemblies of IDPs•Calcium ion switches the symmetry of IDP filaments from C1 to C2•Interfibrillar interactions confer filament bundles as higher-order assemblies Small molecules self-assemble to form higher-order nanostructures that act as functional materials. However, a priori design of small molecules for self-assembly remains a grand challenge due to the limited understanding of the transition from disorder to order and the lack of structures of such assemblies. The guaranteed disorder phase of IDPs makes them the ideal targets for studying disorder-to-order transition in supramolecular assemblies. This work reveals the atomistic structures of the IDP assemblies, a poorly characterized and the most disordered subgroup of peptides, and uses molecular engineering to identify several key factors that contribute to the disorder-to-order transition. Elucidating the driving force, stimuli response, and structures of short IDP assemblies will not only establish IDP sequences as a new molecular platform to build hierarchical superstructures but may also offer useful insights to antagonize pathological IDPs, such as beta-amyloids. Cyro-EM reveals that aromatic packing from pyrenes enables the assemblies of intrinsically disordered peptides (IDPs), and subsequently, molecular engineering indicates