Engineered Design of the E-Helix Structure on Ferritin Nanoparticles

Area of Science:

• Biochemistry
• Structural Biology
• Vaccine Development

Background:

• Ferritin's C-terminus can host immunogenic epitopes for vaccine development.
• Limited understanding exists on how C-terminus modifications affect ferritin stability.
• The E-helix's role in ferritin stabilization is debated.

Purpose of the Study:

• To investigate the role of the C-terminal E-helix in engineered human ferritin heavy chain stability.
• To combine molecular dynamics simulations and experimental methods to engineer ferritin variants for vaccine applications.
• To assess the impact of E-helix modifications on protein folding, stability, and aggregation.

Main Methods:

• Engineered human ferritin heavy chain (F1) with an Epstein-Barr nuclear antigen 1 (EBNA1) epitope and linker (F1L3E1) was used.
• Molecular dynamics simulations (MDS) predicted E-helix hot spots.
• Five variants (C1-C5) were created by modifying electrostatic and hydrophobic interfaces at hot spots.
• Experimental methods confirmed protein folding, stability, and surface hydrophobicity.

Main Results:

• The E-helix is essential for maintaining overall protein stability.
• Modifications to the hydrophobic interface (C3, C4) had a greater impact on folding and stability than electrostatic interface changes (C1, C2).
• Variants C1, C2, and C5 formed stable structures but showed reduced thermal stability; C3 and C4 exhibited significant aggregation due to hydrophobicity changes.

Conclusions:

• The E-helix is critical for the structural integrity of engineered ferritin.
• Careful molecular design of the C-terminus, particularly the E-helix, is vital for developing safe and effective epitope-based chimeric vaccines.
• Minimizing protein aggregation is key to ensuring vaccine safety and efficacy.