Spike glycoprotein bound to ACE2 receptor. PDB 7DF4 (Xu et al. 2020) where ACE2 is cyan and the spike has been colored red, yellow and blue for each subunit of the trimer. This structure has been recently determined at atomic resolution. In spheres, we can see the mutations in the spike glycoprotein from the United Kingdom variant but the only mutation in the receptor binding domain (magenta) is N501Y which is labeled.