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Updated: Jun 5, 2026

Structure of HIV-1 Capsid Assemblies by Cryo-electron Microscopy and Iterative Helical Real-space Reconstruction
Published on: August 9, 2011
Atomic-level modelling of the HIV capsid.
Owen Pornillos1, Barbie K Ganser-Pornillos, Mark Yeager
1Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Researchers determined the X-ray structure of the human immunodeficiency virus type 1 (HIV-1) pentamer, revealing subtle rearrangements and an electrostatic switch controlling capsid assembly. This work enables atomic-level modeling of the complete HIV-1 capsid.
Area of Science:
- Structural Biology
- Virology
- Biochemistry
Background:
- Human immunodeficiency virus type 1 (HIV-1) capsids are fullerene shells made of viral CA protein.
- CA proteins have N- and C-terminal domains (NTD and CTD) that form hexameric/pentameric rings and homodimers, respectively, creating a hexagonal lattice.
- Previous work utilized disulfide crosslinking to crystallize HIV-1 CA hexamers.
Purpose of the Study:
- To determine the X-ray structure of the HIV-1 CA pentamer.
- To understand the structural basis of HIV-1 capsid assembly.
- To enable atomic-level modeling of the complete HIV-1 capsid.
Main Methods:
- Disulfide crosslinking strategy to isolate and crystallize soluble HIV-1 CA pentamers.
- X-ray crystallography at 2.5 Å resolution.
- Analysis of two mutant CA proteins (P17C/T19C and N21C/A22C) to confirm native pentamer structure.
Main Results:
- The X-ray structure of the HIV-1 CA pentamer was solved at 2.5 Å resolution.
- Disulfide-crosslinked mutants recapitulated the native pentamer structure.
- Assembly of hexamers and pentamers involves subtle rearrangements and an electrostatic switch favoring hexamers.
- Rigid-body rotations at assembly interfaces explain lattice curvature.
Conclusions:
- This study completes the structural characterization of HIV-1 capsid substructures.
- The findings provide atomic-level insights into HIV-1 capsid formation.
- The results facilitate comprehensive modeling of the complete HIV-1 capsid structure.
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