Abstract
Rabies virus is an important zoonotic pathogen. Its bullet shaped particle contains a helical nucleocapsid. We used cryo-electron tomography and subsequent subtomogram averaging to determine the structure of its ribonucleoprotein. The resulting electron density map allowed for confident fitting of the N-protein crystal structure, indicating that interactions between neighbouring N-proteins are only mediated by N- and C-terminal protruding subdomains (aa 1–27 and aa 355–372). Additional connecting densities, likely stabilizing the ribonucleoprotein complex, are present between neighbouring M-protein densities on the same helical turn and between M- and N-protein densities located on neighbouring helical turns, but not between M-proteins of different turns, as is observed for the related Vesicular stomatitis virus (VSV). This insight into the architecture of the rabies virus nucleocapsid highlights the surprising structural divergence of large biological assemblies even if the building blocks – here exemplified by VSV M- and N-protein – are structurally closely related.
Highlights
Rabies virus (RABV) is the primary causative agent of rabies in terrestrial mammals
To examine the organisation of the RABV RNP and whether it follows the same architecture as the Vesicular stomatitis virus (VSV) RNP, we determined its structure by cryo electron tomography (CET) and subtomogram averaging on SAD ∆G particles[9], which are a commonly used tool for neuronal tracing[10]
The RABV helical turns deviate by 19° less from the central axis of the virus[5] and are interspaced by an additional 20 Å when compared to VSV
Summary
Rabies virus (RABV) (genus Lyssavirus, family Rhabdoviridiae, order Mononegavirales) is the primary causative agent of rabies in terrestrial mammals. The VSV RNP complex is a helical structure, with each helical turn deviating by 63° from the central axis of the virion. Along the helical turn, neighbouring N-proteins are connected by N- and C- terminally protruding subdomains in a manner similar to the arrangement in the crystal. The interaction between neighbouring M-proteins on the same helical turn is analogous to the interaction pattern observed in the crystal structures of VSV and Lagos bat lyssavirus (LBV) M-protein and mediated (in the case of LBV) by amino acids (aa) 33–36 (MPPP) and aa 112 (W) of the subunit[7]. The RNP structure of VSV is stabilized by interactions of N-proteins on the same and neighbouring helical turn with the N-terminal domain of one M-protein. To examine the organisation of the RABV RNP and whether it follows the same architecture as the VSV RNP, we determined its structure by cryo electron tomography (CET) and subtomogram averaging on SAD ∆G particles[9], which are a commonly used tool for neuronal tracing[10]
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