Flexible, symmetry-directed approach to assembling protein cages

Area of Science:

• Protein engineering
• Biomolecular assembly
• Structural biology

Background:

• Protein self-assembly into large symmetrical structures is common in nature.
• Engineered protein assemblies offer potential in nanotechnology and medicine.
• Designing specific protein-protein interactions for de novo assembly is challenging.

Purpose of the Study:

• To develop a generalizable method for engineering protein assemblies into cage-like structures.
• To utilize de novo designed coiled-coil domains to mediate protein subunit assembly.
• To create well-defined octahedral protein cages.

Main Methods:

• Appending C4-symmetric coiled-coil domains to C3-symmetric esterase trimers via flexible linkers.
• Computational modeling to determine optimal linker length.
• Structural verification using analytical ultracentrifugation, mass spectrometry, and electron microscopy.

Main Results:

• Successfully assembled eight copies of esterase into an octahedral protein cage.
• Optimized linker length was crucial for correct cage formation.
• Demonstrated the importance of flexibility between protein domains for achieving specific geometries.

Conclusions:

• A modular and generalizable approach for protein cage assembly using designed coiled-coil domains has been established.
• This method is adaptable for assembling various proteins into diverse symmetrical structures.
• The findings advance the engineering of protein assemblies for advanced applications.