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Journal of Virology, October 2005, p. 12253-12263, Vol. 79, No. 19
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.19.12253-12263.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Marie Galloux,1,
Joan Pous,3,
Céline Henry,2
Jérôme Denis,4
Bruno Da Costa,1
Jorge Navaza,3
Jean Lepault,3* and
Bernard Delmas1*
Unité de Recherche de Virologie et Immunologie Moléculaires,1 Unité de Biochimie des Protéines, INRA, F-78350 Jouy-en-Josas, France,2 Laboratoire de Virologie Moléculaire et Structurale, UMR 2472 CNRS-INRA, F-91198 Gif-sur-Yvette, France,3 Unité 266 INSERM-URA D1500 CNRS, 4 avenue de l'Observatoire, F-75270 Paris cedex 06, France4
Received 16 March 2005/ Accepted 13 July 2005
The capsid of infectious bursal disease virus (IBDV), a nonenveloped virus of the family Birnaviridae, has a T=13l icosahedral shell constituted by a single protein, VP2, and several disordered peptides, all derived from the precursor pVP2. In this study, we show that two of the peptides, pep11 and pep46, control virus assembly and cell entry. Deletion of pep11 or even simple substitution of most of its residues blocks the capsid morphogenesis. Removal of pep46 also prevents capsid assembly but leads to the formation of subviral particles formed by unprocessed VP2 species. Fitting with the VP2 atomic model into three-dimensional reconstructions of these particles demonstrates that the presence of uncleaved pep46 causes a steric hindrance at the vertices, blocking fivefold axis formation. Mutagenesis of the pVP2 maturation sites confirms that C terminus processing is necessary for VP2 to acquire the correct icosahedral architecture. All peptides present on virions are accessible to proteases or biochemical labeling. One of them, pep46, is shown to induce large structural rearrangements in liposomes and to destabilize target membranes, demonstrating its implication in cell entry.
These authors contributed equally to this work.
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