Structures of respiratory syncytial virus nucleocapsid protein from two crystal forms: details of potential packing interactions in the native helical form

Abstract

Respiratory syncytial virus (RSV) is a frequent cause of respiratory illness in infants, but there is currently no vaccine nor effective drug treatment against this virus. The RSV RNA genome is encapsidated and protected by a nucleocapsid protein; this RNA-nucleocapsid complex serves as a template for viral replication. Interest in the nucleocapsid protein has increased owing to its recent identification as the target site for novel anti-RSV compounds. The crystal structure of human respiratory syncytial virus nucleocapsid (HRSVN) was determined to 3.6 Å resolution from two crystal forms belonging to space groups P2 1 2 1 2 1 and P1, with one and four decameric rings per asymmetric unit, respectively. In contrast to a previous structure of HRSVN, the addition of phosphoprotein was not required to obtain diffraction-quality crystals. The HRSVN structures reported here, although similar to the recently published structure, present different molecular packing which may have some biological implications. The positions of the monomers are slightly shifted in the decamer, confirming the adaptability of the ring structure. The details of the inter-ring contacts in one crystal form revealed here suggest a basis for helical packing and that the stabilization of native HRSVN is via mainly ionic interactions.

Structural Analysis of Respiratory Syncytial Virus Reveals the Position of M2-1 between the Matrix Protein and the Ribonucleoprotein Complex

“…4). The mean RNP width, as determined by center-to-center density measurements, was 11 (Ϯ1.4) nm, correlating with the published crystal structure of nucleocapsid (N) of 10 nm (51,52). In regions where M was absent, neither RNP nor M2-1 was present proximal to the viral membrane.…”

“…However, in some particles, we were able to track the entire RNP. Using the previously determined genome length, pitch, and subunits per helix turn of the hRSV RNP helix (51,52), an average complete genome length of 1.48 m was calculated and used in our analysis.…”

Modulation of Host Immunity by the Human Metapneumovirus

“…The HMPV nucleoprotein (N) shows ϳ41% protein identity to the HRSV N protein (86)(87)(88). The major role of this protein is to package linearized genomic RNA into helical ribonucleoprotein complexes that serve as molecular scaffolds for the assembly of the TR machinery ( Fig.…”

Structure-guided design of small-molecule therapeutics against RSV disease

“…In electron micrographs, the RSV NC displayed a helical structure that is characteristic for members of the Paramyxoviridae family. A crystal structure of the RSV N composed of parallel layers of RSV N:RNA rings was recently solved [37] (Figure 4), and revealed an organization of each N protomer into two core domains, a N-terminal (NTD) and C-terminal (CTD) domain, which are linked via a hinge region (Figure 4). Both the NTD and CTD subunits of each N protomer contain N- and C-terminal extensions, designated N-arm (residues 1–28) and C-arm (residues 360–375), respectively, which interact with neighboring N protomers in a chain-link like arrangement [36].…”

“…Both the NTD and CTD subunits of each N protomer contain N- and C-terminal extensions, designated N-arm (residues 1–28) and C-arm (residues 360–375), respectively, which interact with neighboring N protomers in a chain-link like arrangement [36]. In the crystal structure, RSV N protomers participate in weak top-to-bottom interactions between NTD originating from one helix layer and the CTD of the adjacent layer [37]. The RNA is positioned in a central groove at the NTD/CTD interface, forming a continuous RNA belt along the outside of the NC (Figure 4).…”