One HA protomer (HA1/HA2) of the HA trimer was found in the asymmetric unit. The model was iteratively rebuilt using Coot 56 and refined in Phenix 57.

HA2 sits beneath another domain, a cap known as HA1 that mutates to escape past defenses. Lin explained that HA1 is a common target for flu medications because the exposed cap domain is more ...