Fig. 3: Permissive mutations for NA N336Y in Bil69.

a Locations of natural substitutions from Bil69 to Bil71 are shown as blue spheres on one protomer of NA that is in white cartoon representation, while the other three protomers are shown as semitransparent black surface (PDB 3TIA)²¹. The location of N336Y is shown as an orange sphere. Sialic acid in the active site is shown as yellow sticks. b High-throughput identification of permissive mutations for N336Y in Bil69. The frequency enrichment of each variant in the post-passaged mutant library is shown. The amino acid sequences of variants with at least 2-fold enrichment (log₁₀ enrichment ≥0.3) in the post-passaged mutant libraries of both biological replicates are represented by a sequence logo. c The replication fitness of different Bil69 mutants was examined by a virus rescue experiments. Each bar represents the mean of three independent biological replicates. Each datapoint represents one biological replicate. Virus titer was measured by TCID₅₀. The green dashed line represents the lower detection limit. Source data are provided as a Source data file.