SARS-CoV-2 Encodes a PPxY Late Domain Motif Known to Enhance Budding and Spread in Enveloped RNA Viruses

The current COVID-19 (Coronavirus Disease-2019) pandemic is affecting the health and/or socioeconomic welfare of almost everyone in the world. Finding vaccines and therapeutics is therefore urgent, but elucidation of the molecular mechanisms that allow some viruses to cross host species boundaries, becoming a threat to human health, must also be given close attention. Here, analysis of all proteins of SARS-CoV-2 revealed a unique PPxY Late (L) domain motif, 25PPAY28, in a spike (S) protein inside a predicted hot disordered loop subject to phosphorylation and binding. PPxY motifs in enveloped RNA viruses are known to recruit Nedd4 E3 ubiquitin ligases and ultimately the ESCRT complex to enhance virus budding and release, resulting in higher viral loads, hence facilitating new infections. Interestingly, proteins of SARS-CoV-1 do not feature PPxY motifs, which could explain why SARS-CoV-2 is more contagious than SARS-CoV-1. Should an experimental assessment of this hypothesis show that the PPxY motif plays the same role in SARS-CoV-2 as it does in other enveloped RNA viruses, this motif will become a promising target for the development of novel host-oriented antiviral therapeutics for preventing S proteins from recruiting Nedd4 E3 ubiquitin ligase partners.