Article

Structure and assembly of a paramyxovirus matrix protein.

Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2032, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 08/2012; 109(35):13996-4000. DOI: 10.1073/pnas.1210275109
Source: PubMed

ABSTRACT Many pleomorphic, lipid-enveloped viruses encode matrix proteins that direct their assembly and budding, but the mechanism of this process is unclear. We have combined X-ray crystallography and cryoelectron tomography to show that the matrix protein of Newcastle disease virus, a paramyxovirus and relative of measles virus, forms dimers that assemble into pseudotetrameric arrays that generate the membrane curvature necessary for virus budding. We show that the glycoproteins are anchored in the gaps between the matrix proteins and that the helical nucleocapsids are associated in register with the matrix arrays. About 90% of virions lack matrix arrays, suggesting that, in agreement with previous biological observations, the matrix protein needs to dissociate from the viral membrane during maturation, as is required for fusion and release of the nucleocapsid into the host's cytoplasm. Structure and sequence conservation imply that other paramyxovirus matrix proteins function similarly.

0 Bookmarks
 · 
152 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Paramyxoviruses are a family of negative sense RNA viruses whose members cause serious diseases in humans, such as measles virus, mumps virus and respiratory syncytial virus; and in animals, such as Newcastle disease virus and rinderpest virus. Paramyxovirus particles form by assembly of the viral matrix protein, the ribonucleoprotein complex and the surface glycoproteins at the plasma membrane of infected cells and subsequent viral budding. Two major glycoproteins expressed on the viral envelope, the attachment protein and the fusion protein, promote attachment of the virus to host cells and subsequent virus-cell membrane fusion. Incorporation of the surface glycoproteins into infectious progeny particles requires coordinated interplay between the three viral structural components, driven primarily by the matrix protein. In this review, we discuss recent progress in understanding the contributions of the matrix protein and glycoproteins in driving paramyxovirus assembly and budding while focusing on the viral protein interactions underlying this process and the intracellular trafficking pathways for targeting viral components to assembly sites. Differences in the mechanisms of particle production among the different family members will be highlighted throughout.
    Viruses. 01/2014; 6(8):3019-3054.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Paramyxoviruses contain a bi-lipidic envelope decorated by two transmembrane glycoproteins and carpeted on the inner surface with a layer of matrix proteins (M), thought to bridge the glycoproteins with the viral nucleocapsids. To characterize M structure-function features, a set of M domains were mutated or deleted. The genes encoding these modified M were incorporated into recombinant Sendai viruses and expressed as supplemental proteins. Using a method of integrated suppression complementation system (ISCS), the functions of these M mutants were analyzed in the context of the infection. Cellular membrane association, localization at the cell periphery, nucleocapsid binding, cellular protein interactions and promotion of viral particle formation were characterized in relation with the mutations. At the end, lack of nucleocapsid binding go together with lack of cell surface localization and both features definitely correlate with loss of M global function estimated by viral particle production.
    Virology. 01/2014; s 464–465:330–340.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Human respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and pneumonia in infants and elderly worldwide; however there is no licensed RSV vaccine or effective drug treatment available. The RSV Matrix (M) protein plays key roles in virus assembly and budding, but the protein interactions that govern budding of infectious virus are not known. In this study we focus on M protein and identify a key phosphorylation site (Thr(205)) in M that is critical for RSV infectious virus production. Recombinant virus with a nonphosphorylatable Alanine (Ala) residue at the site was markedly attenuated, whereas virus with a phosphomimetic Aspartate (Asp) resulted in a non-viable virus which could only be recovered with an additional mutation in M (Serine to Asparagine at position 220), strongly implying that Thr(205) is critical for viral infectivity. Experiments in vitro showed that mutation of Thr(205) does not affect M stability or the ability to form dimers, but implicate an effect on higher order oligomer assembly. In transfected and infected cells, Asp substitution of Thr(205) appeared to impair M oligomerization; typical filamentous structures still formed at the plasma membrane, but M assembly during the ensuing elongation process seemed to be impaired, resulting in shorter and more branched filaments as observed using EM. Our data thus imply for the first time that M oligomerization, regulated by negative charge at Thr(205), may be critical to production of infectious RSV. We show here for the first time that RSV M's role in virus assembly/release is strongly dependent on threonine (Thr(205)), a consensus site for CK2, which appears to play a key regulatory role in modulating M oligomerization and association with virus filaments. Our analysis indicates that T205 mutations do not impair M dimerization or virus-like filament formation per se, but rather the ability of M to assemble in ordered fashion on the viral filaments themselves. This appears to impact in turn upon the infectivity of released virus, rather than on virus production or release itself. Thus, M oligomerization would appear to be a target of interest for the development of anti-RSV agents; further, the recombinant T(205)-substituted mutant viruses described here would appear to be the first RSV mutants affected in viral maturation to our knowledge, and hence of considerable interest for vaccine approaches in the future.
    Journal of Virology 03/2014; · 5.08 Impact Factor

Full-text (2 Sources)

Download
15 Downloads
Available from
May 21, 2014