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Effect of mutations in capsid shell protein on the assembly of BmCPV virus-like particles

Feifei Ren1,2, Luc Swevers1, Qiuyuan Lu2

  • 1Insect Molecular Genetics and Biotechnology, Institute of Biosciences and Applications, National Centre for Scientific Research Demokritos, Aghia Paraskevi, Athens, Greece.

The Journal of General Virology
|December 17, 2020
PubMed

Insights

The small protrusion domain (SPD) of Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) capsid shell protein (CSP) is crucial for viral capsid assembly. Mutating three key sites in the SPD significantly impacts VLP assembly, highlighting its essential role.

Area of Science:

  • Virology
  • Structural Biology
  • Molecular Biology

Background:

  • Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a dsRNA virus with a single-layer capsid, belonging to the Cypovirus genus.
  • The BmCPV capsid is composed of asymmetric units containing turret protein (TP), large protrusion proteins (LPP), and capsid shell proteins (CSP).
  • Capsid shell proteins (CSP) can self-assemble into virus-like particles (VLPs), with the small protrusion domain (SPD) potentially vital for capsid assembly.

Purpose of the Study:

  • To investigate the role of specific amino acid sites within the small protrusion domain (SPD) of CSP in BmCPV VLP assembly.
  • To analyze the impact of point mutations in the SPD on the efficiency and morphology of VLP formation.

Main Methods:

  • Site-directed mutagenesis was used to introduce point mutations at three critical amino acid sites (D828, S829, V945) in the SPD of CSP.
  • A multi-gene expression system (Ac-MultiBac baculovirus) was employed to produce recombinant VLPs in vitro.
  • Transmission electron microscopy (TEM) was utilized to assess the assembly efficiency and morphology of the generated VLPs.

Main Results:

  • Single and double site mutations in the SPD had minimal effects on VLP assembly efficiency and morphology.
  • Simultaneous mutation of the three critical amino acid sites (D828, S829, V945) significantly impacted VLP assembly.
  • The experimental data confirm the essential role of the SPD in the self-assembly of the BmCPV viral capsid.

Conclusions:

  • The small protrusion domain (SPD) of the capsid shell protein (CSP) is indispensable for the proper assembly of Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) capsids.
  • Understanding the function of the SPD provides a foundation for further elucidating the molecular and structural mechanisms governing BmCPV capsid assembly.
  • This study contributes to the knowledge of viral assembly processes, particularly for dsRNA viruses in the Reoviridae family.
Keywords:
Bombyx moricytoplasmic polyhedrosis virussite-directed mutagenesisvirus-like particles

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