N501Y denotes a change from asparagine (N) to tyrosine (Y) in amino-acid position 501.

This change is believed by PHE to increase binding affinity because of its position inside the spike glycoprotein's receptor-binding domain, which binds ACE2 in human cells; data also support the hypothesis of increased binding affinity from this change. Variants with N501Y include P.1 (Brazil/Japan), Variant of Concern 202012/01 (UK), 501.V2 (South Africa), and COH.20G/501Y (Columbus, Ohio). This last became the dominant form of the virus in Columbus in late December 2020 and January and appears to have evolved independently of other variants.