Surpassing protein specificity in biomimetics of bacterial amyloids

In nature, nontoxic protein amyloids serve as dynamic, protein-specific depots, exemplified by both bacterial inclusion bodies and secretory granules from the endocrine system. Inspired by these systems, chemically defined and regulatory-compliant artificial protein microgranules have been developed for clinical applications as endocrine-like protein repositories. This has been achieved by exploiting the reversible coordination between histidine residues and divalent cations such as Zn⁺², that promotes protein-protein interactions. While stereospecificity is a main architectonic feature of natural amyloids, the potential for synthetic approaches to create hybrid protein materials remains unexplored. Such materials could enable the occurrence and synchronized local application of diverse proteins in predefined molar ratios, for coupled enzymatic reactions or delivery of synergistically acting polypeptides. Here, we report on the fabrication of artificial protein granules with amyloidal architecture formed by combining two structurally distinct polypeptides. Specifically, we tested co-aggregation of the pairs GFP/IRFP and GFP/β-galactosidase. The formation of hybrid microparticles was confirmed through FRET and complementary methodologies, demonstrating that the His-Zn clustering technology does not require sequential or structural homologies between aggregating polypeptides. This approach opens new avenues for the development of functional depots that capitalize on synergistic protein functionalities, paving the way for next-generation functional materials.