The recent emergence of a novel coronavirus associated with an ongoing outbreak of pneumonia (Covid-2019) resulted in infections of more than 72,000 people and claimed over 1,800 lives. Coronavirus spike (S) glycoprotein trimers promote entry into cells and are the main target of the humoral immune response. We show here that SARS-CoV-2 S mediates entry in VeroE6 cells and in BHK cells transiently transfected with human ACE2, establishing ACE2 as a functional receptor for this novel coronavirus. We further demonstrate that the receptor-binding domains of SARS-CoV-2 S and SARS-CoV S bind with similar affinities to human ACE2, which correlates with the efficient spread of SARS-CoV-2 among humans. We found that the SARS-CoV-2 S glycoprotein harbors a furin cleavage site at the boundary between the S 1 /S 2 subunits, which is processed during biogenesis and sets this virus apart from SARS-CoV and other SARS-related CoVs. We determined a cryo-electron microscopy structure of the SARS-CoV-2 S ectodomain trimer, demonstrating spontaneous opening of the receptor-binding domain, and providing a blueprint for the design of vaccines and inhibitors of viral entry. Finally, we demonstrate that SARS-CoV S murine polyclonal sera potently inhibited SARS-CoV-.

SUMMARY Histone demethylases LSD1 and LSD2 (KDM1A/B) catalyze the oxidative demethylation of Lys4 of histone H3. We employed molecular dynamics simulations to probe the diffusion of the oxygen substrate. Oxygen can reach the catalytic centre independently from the presence of a bound histone peptide, implying that LSD1 can complete subsequent demethylation cycles without detaching from the nucleosomal particle. The simulations highlight the role of a strictly conserved active-site Lys residue providing general insight into the enzymatic mechanism of oxygen-reacting flavoenzymes. The crystal structure of LSD1-CoREST bound to a peptide of the transcription factor SNAIL1 unravels a fascinating example of molecular mimicry. The SNAIL1 N-terminal residues bind to the enzyme active-site cleft, effectively mimicking the H3 tail. This finding predicts that other members of the SNAIL/Scratch transcription factor family might associate to LSD1/2. The combination of selective histone-modifying activity with the distinct recognition mechanisms underlies the biological complexity of LSD1/2.

Three highly pathogenic β-coronaviruses crossed the animal-to-human species barrier in the past two decades: SARS-CoV, MERS-CoV and SARS-CoV-2. SARS-CoV-2 has infected more than 64 million people worldwide, claimed over 1.4 million lives and is responsible for the ongoing COVID-19 pandemic. We isolated a monoclonal antibody, termed B6, cross-reacting with eight β-coronavirus spike glycoproteins, including all five human-infecting β-coronaviruses, and broadly inhibiting entry of pseudotyped viruses from two coronavirus lineages. Cryo-electron microscopy and X-ray crystallography characterization reveal that B6 binds to a conserved cryptic epitope located in the fusion machinery and indicate that antibody binding sterically interferes with spike conformational changes leading to membrane fusion. Our data provide a structural framework explaining B6 cross-reactivity with β-coronaviruses from three lineages along with proof-of-concept for antibody-mediated broad coronavirus neutralization elicited through vaccination. This study unveils an unexpected target for next-generation structure-guided design of a pan-coronavirus vaccine.