The structure of the nucleoprotein of Influenza D shows that all Orthomyxoviridae nucleoproteins have a similar NP(CORE), with or without a NP(TAIL) for nuclear transport

This paper focuses on the nucleoprotein (NP) of the newly identified member of the Orthomyxoviridae family, Influenza D virus. To date several X-ray structures of NP of Influenza A (A/NP) and B (B/NP) viruses and of infectious salmon anemia (ISA/NP) virus have been solved. Here we purified, characterized and solved the X-ray structure of the tetrameric D/NP at 2.4 Å resolution. The crystal structure of its core is similar to NP of other Influenza viruses. However, unlike A/NP and B/NP which possess a flexible amino-terminal tail containing nuclear localization signals (NLS) for their nuclear import, D/NP possesses a carboxy-terminal tail (D/NP(TAIL)). We show that D/NP(TAIL) harbors a bipartite NLS and designed C-terminal truncated mutants to demonstrate the role of D/NP(TAIL) for nuclear transport.