Local Microenvironments of capsomer variants in the PBCV-1

Area of Science:

• Virology
• Structural Biology
• Biophysics

Background:

• The giant virus PBCV-1, a member of the Nucleocytoviricota virus (NCV) group, has had its structure resolved to near atomic resolution.
• Its capsid is primarily composed of Type I capsomers, with five other variant types identified.
• The function of certain variants, like Type V capsomers found at specific locations, remains largely unknown.

Purpose of the Study:

• To investigate the functional roles of Type V capsomers within the PBCV-1 capsid.
• To compare the interaction properties of Type V capsomers with the more common Type I capsomers.
• To analyze the interactions between these capsomer variants and their local capsid microenvironment.

Main Methods:

• Structural analysis of PBCV-1 capsid components.
• Experimental replacement of Type V capsomers with Type I capsomers.
• Investigation of inter-capsomer binding forces and electrostatic interactions.

Main Results:

• Significant differences were observed between Type V and Type I capsomers.
• Type V capsomers displayed a stronger binding affinity to neighboring capsomers compared to Type I.
• Salt bridges and key residues involved in Type V/I capsomer interactions were identified, consistent with electrostatic calculations.

Conclusions:

• Type V capsomers play a distinct role in viral capsid stability due to stronger binding interactions.
• Understanding the specific interactions within local capsid microenvironments is crucial for deciphering viral assembly mechanisms.
• This research provides insights into the structural diversity and assembly principles of giant viruses.