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Updated: May 5, 2026
12:38
Structure of HIV-1 Capsid Assemblies by Cryo-electron Microscopy and Iterative Helical Real-space Reconstruction
Published on: August 9, 2011
19.1K
Visualization of a missing link in retrovirus capsid assembly.
Giovanni Cardone1, John G Purdy, Naiqian Cheng
1Laboratory of Structural Biology, National Institute for Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nature
|February 6, 2009
Summary
Researchers observed Rous sarcoma virus capsids using cryo-electron microscopy, confirming the fullerene conjecture. This study reveals how pentamers and hexamers of capsid protein assemble into icosahedral structures, crucial for retroviral infectivity.
Area of Science:
- Structural biology
- Virology
- Biophysics
Background:
- Retrovirus infectivity depends on a well-formed capsid.
- Retrovirus capsids exhibit unusual structural variability.
- The fullerene conjecture proposes capsids are made of hexamers and pentamers of capsid protein (CA).
Purpose of the Study:
- To investigate the in vitro assembly of retroviral capsids.
- To experimentally validate the fullerene conjecture regarding capsid protein (CA) arrangement.
- To elucidate the structural role of pentamers and hexamers in Rous sarcoma virus capsid formation.
Main Methods:
- Cryo-electron microscopy was used to analyze in vitro-assembled Rous sarcoma virus capsids.
- Atomic models of capsid protein (CA) domains were fitted into cryo-EM reconstructions.
- Analysis focused on the arrangement of hexamers and pentamers within icosahedral capsid structures.
Main Results:
- Two icosahedrally symmetric capsids were observed: one with 12 pentamers, and another with 12 pentamers and 20 hexamers.
- Fitting of atomic models revealed three distinct inter-subunit interactions.
- The study confirmed the presence and arrangement of pentamers at capsid vertices.
Conclusions:
- The findings substantiate the fullerene conjecture for retroviral capsids.
- Pentamer accommodation at vertices and the role of nucleation in capsid morphology are supported.
- Electrostatic interactions are implied to regulate the differential assembly of pentamers and hexamers.
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