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The PM2 virion has a novel organization with an internal membrane and pentameric receptor binding spikes

Juha T Huiskonen1, Hanna M Kivelä, Dennis H Bamford

  • 1Institute of Biotechnology, University of Helsinki, Helsinki, Finland.

Nature Structural & Molecular Biology
|August 3, 2004
PubMed

Insights

Cryo-electron microscopy of bacteriophage PM2 reveals its internal membrane structure. This viral membrane acts as a scaffold for capsid assembly and facilitates genome entry through host membrane fusion.

Area of Science:

  • Structural biology
  • Virology
  • Biophysics

Background:

  • Biological membranes pose significant challenges for in situ structural analysis.
  • Membrane-containing viruses, like bacteriophage PM2, offer unique models due to their constrained membrane within an icosahedral capsid.

Purpose of the Study:

  • To determine the in situ structure of the bacteriophage PM2 membrane and capsid.
  • To elucidate the roles of the viral membrane in bacteriophage assembly and infection.

Main Methods:

  • Cryo-electron microscopy (Cryo-EM) and image reconstruction were employed.
  • High-resolution structural analysis of the bacteriophage PM2 capsid and associated membrane.

Main Results:

  • A detailed structure of the bacteriophage PM2 capsid at 8.4 Å resolution was obtained, revealing 200 trimeric capsomers with pseudo T = 21 organization.
  • The viral membrane forms a bilayer lining the inner surface of the capsid, with the genome interacting with the inner leaflet.
  • Pentameric spikes involved in receptor binding were identified on the capsid surface.

Conclusions:

  • The bacteriophage PM2 membrane serves as a scaffold for capsid assembly.
  • The membrane facilitates genome entry into the host cell via fusion with the host outer membrane.
  • The structure provides insights into viral DNA packaging and release mechanisms.

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