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Updated: Jun 10, 2026

Simple and Robust in vivo and in vitro Approach for Studying Virus Assembly
Published on: March 1, 2012
Structure of a Venezuelan equine encephalitis virus assembly intermediate isolated from infected cells
Kristen Lamb1, G L Lokesh, Michael Sherman
1Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-0647, USA.
Abstract:
Venezuelan equine encephalitis virus (VEEV) is a prototypical enveloped ssRNA virus of the family Togaviridae. To better understand alphavirus assembly, we analyzed newly formed nucleocapsid particles (termed pre-viral nucleocapsids) isolated from infected cells. These particles were intermediates along the virus assembly pathway, and ultimately bind membrane-associated viral glycoproteins to bud as mature infectious virus. Purified pre-viral nucleocapsids were spherical with a unimodal diameter distribution. The structure of one class of pre-viral nucleocapsids was determined with single particle reconstruction of cryo-electron microscopy images. These studies showed that pre-viral nucleocapsids assembled into an icosahedral structure with a capsid stoichiometry similar to the mature nucleocapsid. However, the individual capsomers were organized significantly differently within the pre-viral and mature nucleocapsids. The pre-viral nucleocapsid structure implies that nucleocapsids are highly plastic and undergo glycoprotein and/or lipid-driven rearrangements during virus self-assembly. This mechanism of self-assembly may be general for other enveloped viruses.
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