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Molecular organization of Mason-Pfizer monkey virus capsids assembled from Gag polyprotein in Escherichia coli

Milan V Nermut1, Patrick Bron, Daniel Thomas

  • 1National Institute for Biological Standards and Control, South Mimms, Hertfordshire EN6 3QG, United Kingdom. mvnermut@nibsc.ac.uk

Journal of Virology
|April 5, 2002
PubMed

Insights

Researchers studied Mason-Pfizer monkey virus Gag protein shells using electron microscopy. They found that trimers of truncated Gag proteins form the basic building block of the capsid network.

Area of Science:

  • Structural biology
  • Virology
  • Biochemistry

Background:

  • Mason-Pfizer monkey virus (MPMV) is a retrovirus.
  • Gag polyprotein self-assembles into immature capsid structures.
  • Understanding Gag protein assembly is crucial for viral structure research.

Purpose of the Study:

  • To investigate the assembly of Gag protein shells from truncated Gag precursors.
  • To determine the basic building block of the Gag protein network.
  • To elucidate the role of the CA domain in Gag trimerization.

Main Methods:

  • Electron microscopy (negative staining and freeze-etching).
  • Image processing of assembled Gag protein shells.
  • Assembly of virus-like particles from truncated Gag proteins in E. coli.

Main Results:

  • Truncated Gag proteins (Deltap4Gag and Pro(-)CA.NC) assembled into capsids with a hexagonal network of holes.
  • The center-to-center spacing of holes was approximately 7.1-7.4 nm.
  • Image processing revealed that trimers of truncated Gag proteins form the basic building block of the capsid network.

Conclusions:

  • The trimer of Gag domains is the fundamental unit of the cage-like network.
  • The CA domain plays a critical role in trimeric interactions of the Gag polyprotein.
  • Structural constraints within the CA domain influence Gag protein assembly.

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