Dynamic Assembly of Pentamer-Based Protein Nanotubes

Area of Science:

• Biochemistry
• Structural Biology
• Nanotechnology

Background:

• Hollow protein particles serve as versatile nanocontainers for applications in delivery and catalysis.
• Understanding the assembly principles of protein structures is crucial for designing functional nanomaterials.

Purpose of the Study:

• To investigate the assembly mechanisms of a circularly permuted enzyme, Aquifex aeolicus lumazine synthase (cpAaLS).
• To explore how ionic strength influences the morphology of cpAaLS assemblies.
• To provide a theoretical and structural basis for designing protein-based nanoarchitectures.

Main Methods:

• Cryogenic electron microscopy (cryo-EM) was used to determine the structures of assembled particles.
• Circular permutation of Aquifex aeolicus lumazine synthase was employed.
• Mathematical modeling was utilized to analyze subunit interactions and predict assembly patterns.

Main Results:

• cpAaLS self-assembles into hollow spherical and cylindrical structures, adapting to varying ionic strengths.
• These structures are exclusively composed of pentameric subunits.
• The transformation from cages to tubes is driven by hindered 3-fold symmetry interactions and subunit torsion angles, mediated by an altered α-helix domain.
• Mathematical models identified double- and triple-stranded helical arrangements as optimal tiling patterns.

Conclusions:

• The study reveals dynamic assembly principles of pentamer-based protein cages and nanotubes.
• Structural insights provide guidelines for engineering protein nanoarchitectures with tailored morphology and assembly properties.
• Circular permutation offers a strategy to control protein assembly and create novel nanostructures.