Structural peptides of a nonenveloped virus are involved in assembly and membrane translocation.
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.
Chevalier
Christophe
C
Unité de Recherche de Virologie et Immunologie Moléculaires, INRA, F-78350 Jouy-en-Josas, France.
Galloux
Marie
M
Pous
Joan
J
Henry
Céline
C
Denis
Jérôme
J
Da Costa
Bruno
B
Navaza
Jorge
J
Lepault
Jean
J
Delmas
Bernard
B
D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D002463:Cell Membrane Permeability; D006461:Hemolysis; D006801:Humans; D007243:Infectious bursal disease virus / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D008081:Liposomes; D008854:Microscopy, Electron; D009154:Mutation; D010455:Peptides / Q000502:physiology; D017384:Sequence Deletion; D015678:Viral Structural Proteins / Q000235:genetics* / Q000502:physiology*; D014771:Virion / Q000648:ultrastructure; D019065:Virus Assembly / Q000502:physiology*
D008081:Liposomes; D010455:Peptides; C082513:VP2 protein, infectious bursal disease virus; D015678:Viral Structural Proteins