Crystal structure of the SARS-CoV-2 non-structural protein 9, Nsp9

Dene Littler; Benjamin Gully; Rhys N Colson; Jamie Rossjohn

Here we describe the structure of the recombinantly expressed Nsp9COV19 as part of a global effort to characterise the virus causing a current global pandemic. Nsp9 is important for virulence in SARS-CoV (Miknis et al., 2009) . It remains to be understood whether Nsp9COV19 plays a similar role in SARS-CoV-2, however the 97 % sequence identity suggests a high degree of functional conservation. The CoV Nsp9 proteins are seemingly obligate dimers comprising a unique fold that associates via an unusual a-helical GxxxG interaction motif. The integrity of this motif is considered important for viral replication (Miknis et al., 2009 ), leading to a proposal that disruption of the unusual dimer interface impacts on RNA binding and function (Hu et al., 2017) . Mutation of the same interaction motif in the porcine delta coronavirus Nsp9PDCoV also disrupted nucleotide binding capacity (Zeng et al., 2018) .