Co-Assembly Tags Based on Charge Complementarity (CATCH) for Installing Functional Protein Ligands into Supramolecular Biomaterials

Abstract

Installing folded proteins into biomaterials is gaining interest for imparting functional properties that often cannot be provided by unfolded peptides or small molecules, such as catalysis, antigen conformation, or molecular recognition. Although covalent grafting provides a simple means to immobilize proteins onto pre-formed biomaterials, amenable chemistries can alter protein bioactivity, are relatively non-specific, and can be difficult to reproduce. Covalent fusions of bioactive molecules and synthetic peptides that can self-assemble into nano-scale architectures are a promising alternative for creating functional supramolecular biomaterials with precise and reproducible composition. Here we created a pair of oppositely charged synthetic peptides, referred to as “CATCH” (Co-Assembly Tags based on CHarge complementarity), to install folded proteins into supramolecular biomaterials. CATCH peptides co-assemble into β-sheet nanofibers when combined, yet cannot assemble independently due to electrostatic repulsion. Electrostatically controlled assembly enabled high yield production of soluble CATCH-green fluorescent protein (CATCH(−)GFP) by E. coli. Binary mixtures of CATCH-GFP and its charge-complementary peptide self-assembled into fluorescent microparticles, whereas ternary mixtures of CATCH(−)GFP and both CATCH peptides self-assembled into fluorescent nanofibers and macroscopic hydrogels. The CATCH system is therefore likely to be broadly useful for creating functional supramolecular biomaterials with integrated folded protein components for various biomedical and biotechnological applications.