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Title of the thesis: Harnessing biomolecular click reactions for modular protein engineering and functionalization

Thesis defender: Ruxia Fan 
Opponent: Prof. Jan Johansson, Karolinska Institute, Sweden 
Custos: Assistant Prof. Sesilja Aranko, Aalto University School of Chemical Engineering

Harnessing biomolecular click reactions for modular protein engineering and functionalization
 

Proteins are essential building blocks for advanced biological and bioinspired materials due to their extraordinary structural diversity, modularity, and functional versatility. However, fully harnessing the potential of proteins remains challenging. Biomolecular click reactions offer promising solutions by expanding the ligation toolkit with genetically encodable, efficient reactions, thereby facilitating reliable and modular protein assembly and functionalization.

This thesis focuses on protein engineering using biomolecular click reactions, specifically the development and application of a new Catcher/Tag protein ligation system (SilkCatcher/SilkTag) for modular protein assembly and functionalization, using spider-silk-like proteins as model building blocks. The research established a minimal Catcher/Tag pair capable of efficient and orthogonal covalent protein ligation. Leveraging the structural affinity and covalent reactivity between Catcher domains and Tag peptides, a versatile platform was created to support multi-fragment protein conjugation, enzyme immobilization, protein purification, site-specific fiber functionalization, and controlled polyphosphorylation of spider-silk-like proteins. Furthermore, the solubility-enhancing properties of the Catcher domain improved the expression of aggregation-prone proteins, enabling efficient production of spider-silk-like proteins and the development of an aqueous spinning system for production of artificial spider silk fibers with outstanding extensibility and toughness.

Overall, this thesis demonstrates that the Catcher/Tag-mediated biomolecular click reactions provide a versatile and modular platform for protein engineering. Their efficient covalent ligation and strict orthogonality enable controlled protein assembly, targeted immobilization, and precise functional modification. These studies highlight the broad potential of biomolecular click reactions for advanced protein engineering and their use for the development of functional biomaterials.

 
biomolecular click reaction, Catcher/Tag, spider silk, modular protein assembly, functionalization

Thesis available for public display 7 days prior to the defence at .

Contact information: ruxia.fan@aalto.fi

LinkedIn: https://www.linkedin.com/in/ruxia-fan-5a09171a4/?originalSubdomain=fi
Cellular engineering group: /en/department-of-bioproducts-and-biosystems/cellular-engineering