Design of an In-Cell Protein Crystal for the Environmentally Responsive Construction of a Supramolecular Filament

Protein assemblies can be designed for development of nano-bio materials. This has been achieved by modulating protein-protein interactions. However, fabrication of highly ordered protein assemblies remains challenging. Protein crystals, which have highly ordered arrangements of protein molecules, provide useful source matrices for synthesizing artificial protein assemblies. Here, we describe construction of a supramolecular filament structure by engineering covalent and non-covalent interactions in a protein crystal. Performing in-cell crystallization of Trypanosoma brucei cysteine protease cathepsin B (TbCatB), we achieved a precise arrangement of protein molecules while suppressing random aggregation due to disulfide bonds. We succeeded in synthesizing bundled filament from the crystals by autoxidation of cysteinyl thiols after the isolation of the crystals from living cells.

Automated summary

Protein assemblies can be designed using protein crystals with highly ordered arrangements of protein molecules, which serve as useful matrices for synthesizing artificial protein assemblies. By engineering covalent and non-covalent interactions in a protein crystal, a supramolecular filament structure was constructed to achieve precise arrangement of protein molecules and prevent random aggregation caused by disulfide bonds. The successful synthesis of bundled filament from the crystals was accomplished by autoxidation of cysteinyl thiols after isolation from living cells.