Biochemical and Biophysical Research Communications, Vol.538, 54-62, 2021
High-resolution structure and biophysical characterization of the nucleocapsid phosphoprotein dimerization domain from the Covid-19 severe acute respiratory syndrome coronavirus 2
Unprecedented by number of casualties and socio-economic burden occurring worldwide, the corona virus disease 2019 (Covid-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the worst health crisis of this century. In order to develop adequate countermeasures against Covid-19, identification and structural characterization of suitable antiviral targets within the SARS-CoV-2 protein repertoire is urgently needed. The nucleocapsid phosphoprotein (N) is a multifunctional and highly immunogenic determinant of virulence and pathogenicity, whose main functions consist in oligomerizing and packaging the single-stranded RNA (ssRNA) viral genome. Here we report the structural and biophysical characterization of the SARS-CoV-2 N C-terminal domain (CTD), on which both N homo-oligomerizati on and ssRNA binding depend. Crystal structures solved at 1.44 angstrom and 1.36 angstrom resolution describe a rhombus-shape N CTD dimer, which stably exists in solution as validated by size exclusion chromatography coupled to multi-angle light scattering and analytical ultracentrifugation. Differential scanning fluorimetry revealed moderate thermal stability and a tendency towards conformational change. Microscale thermophoresis demonstrated binding to a 7-bp SARS-CoV-2 genomic ssRNA fragment at micromolar affinity. Furthermore, a low-resolution preliminary model of the fulllength SARS-CoV N in complex with ssRNA, obtained by cryo-electron microscopy, provides an initial understanding of self-associating and RNA binding functions exerted by the SARS-CoV-2 N. (c) 2020 Elsevier Inc. All rights reserved.