Solution Structures of Engineered Vault Particles.

Area of Science:

• Structural Biology
• Biochemistry
• Protein Engineering

Background:

• Prior crystal structures of vaults offered limited insights into their conformational flexibility due to crystal packing artifacts.
• Understanding vault structure is crucial for elucidating their biological functions and therapeutic applications.

Purpose of the Study:

• To determine the near-atomic resolution structures of engineered vaults in a non-crystalline environment.
• To resolve discrepancies in previous vault structural models and characterize solution-phase conformations.
• To assess the potential of engineered vaults for drug delivery applications.

Main Methods:

• Engineered rat major vault protein (MVP) with an N-terminal HIV-1 Gag protein segment.
• Determined vault structures at approximately 4.8 Å resolution in solution using cryo-EM or similar techniques.
• Analyzed vault structures to identify distinct conformations and their structural features.

Main Results:

• Vaults in solution adopt two distinct conformations (Conformation 1 and Conformation 2), both exhibiting D39 symmetry.
• Conformation 2 displays a significant translocation (up to 10 Å) of the shoulder region compared to Conformation 1 and prior crystal structures.
• The N-terminal Gag-loaded extension shows internal disposition and flexibility, suggesting potential for cargo loading at the vault's barrel waist.

Conclusions:

• The study provides the first high-resolution structures of vaults in solution, clarifying structural variability and resolving discrepancies in prior models.
• The identified conformations highlight the inherent flexibility of the vault structure.
• Engineered vaults demonstrate promising potential as drug delivery vehicles due to the adaptable internal structure for cargo.