title: Structure of Schmallenberg orthobunyavirus nucleoprotein suggests a novel mechanism of genome encapsidation.
abstract: Schmallenberg virus (SBV), a newly emerged orthobunyavirus (family Bunyaviridae), has spread rapidly across Europe and has caused congenital abnormalities in the offspring of cattle, sheep, and goats. Like other orthobunyaviruses, SBV contains a tripartite negative-sense RNA genome that encodes four structural and two nonstructural proteins. The nucleoprotein (N) encapsidates the three viral genomic RNA segments and plays a crucial role in viral RNA transcription and replication. Here we report the crystal structure of the bacterially expressed SBV nucleoprotein to a 3.06-Å resolution. The protomer is composed of two domains (N-terminal and C-terminal domains) with flexible N-terminal and C-terminal arms. The N protein has a novel fold and forms a central positively charged cleft for genomic RNA binding. The nucleoprotein purified under native conditions forms a tetramer, while the nucleoprotein obtained following denaturation and refolding forms a hexamer. Our structural and functional analyses demonstrate that both N-terminal and C-terminal arms are involved in N-N interaction and oligomerization and play an essential role in viral RNA synthesis, suggesting a novel mechanism for viral RNA encapsidation and transcription.
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Haohao
authors.initials: H
authors.lastname: Dong
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Richard M
authors.initials: RM
authors.lastname: Elliott
authors.forename: Changjiang
authors.initials: C
authors.lastname: Dong
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009698:Nucleoproteins / Q000737:chemistry*; D016851:Orthobunyavirus / Q000737:chemistry* / Q000502:physiology*; D011487:Protein Conformation; D055503:Protein Multimerization; D016601:RNA-Binding Proteins / Q000737:chemistry; D016415:Sequence Alignment; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D009698:Nucleoproteins; D016601:RNA-Binding Proteins