Inside polyomavirus at 25-A resolution.

Area of Science:

• Structural biology
• Virology
• Biochemistry

Background:

• Polyomavirus capsids are icosahedral structures composed of VP1 pentamers.
• The precise arrangement and internal components of polyomavirus virions remain incompletely understood.

Purpose of the Study:

• To determine the internal structure of the polyomavirus virion using X-ray diffraction.
• To identify the location and potential role of internal viral proteins (VP2 and VP3).

Main Methods:

• Difference Fourier analysis of X-ray diffraction data at 25-Å resolution.
• Crystallization of empty polyomavirus capsids and complete virions.
• Analysis of self-assembly of purified recombinant VP1.

Main Results:

• Isomorphous crystallization of empty capsids and complete virions.
• Electron density map revealing 72 prongs extending from the core into VP1 pentamer cavities.
• Identification of these prongs with VP2 and VP3 molecules.

Conclusions:

• VP2 and VP3 molecules are located within the polyomavirus capsid, interacting with VP1 pentamers.
• These internal proteins may play a role in guiding capsid assembly onto the nucleohistone core.
• The core itself shows no regular order in the electron density map.