pH-induced morphological changes of proteinaceous viral shells

Area of Science:

• Structural biology
• Biophysics
• Virology

Background:

• Environmental pH variations can induce significant morphological changes in bacteriophage protein shells.
• These in vitro changes resemble in vivo capsid alterations during DNA packaging.
• Simple elastic models are insufficient to explain these observed shape and size modifications.

Purpose of the Study:

• To develop a theoretical framework explaining pH-induced viral capsid morphological changes.
• To integrate shell elasticity with pH-dependent charge distribution in a unified model.
• To elucidate the mechanism of bacteriophage maturation and pH-driven state transitions.

Main Methods:

• Developed a theoretical model combining thin icosahedral shell elasticity and electrostatic free energy.
• Incorporated pH-dependent capsid charge distribution into the energy minimization framework.
• Utilized in vitro shell reconstructions of bacteriophage HK97 for analysis.

Main Results:

• The theoretical model predicts equilibrium viral shell shapes based on elasticity and protein charge configuration.
• The model successfully explains pH-induced transitions between Prohead II and Expansion Intermediate II states in HK97.
• Identified key factors governing bacteriophage maturation and morphological dynamics.

Conclusions:

• A combined elastic and electrostatic model accurately describes pH-dependent viral capsid morphology.
• Bacteriophage maturation involves reversible transitions driven by environmental pH changes.
• The study provides insights into the physical principles governing viral structure and assembly.