Fig. 2

Compensatory mutations for the deleterious effect of D190E in Bris07 HA. a Substitutions that represent reversions from Bris07 to Wy03 are highlighted in pink or cyan. Pink: residues included in the deep mutational scanning experiment. Cyan: residues not characterized in this study. Purple: residue 190. The receptor analog LS-tetrasaccharide c (LSTc) is colored in yellow. PDB 2YP4 (ref. ⁹). b Potential compensatory substitutions of Bris07 D190E were probed by deep mutational scanning. Each datapoint represents a certain combination of substitutions. The position along the y-axis represents the log₁₀ RF index for the indicated combination of substitutions plus D190E, whereas position along the x-axis represents the log₁₀ RF index for the indicated combination of substitutions by themselves (without D190E). c Effect of different combinations of substitutions on Bris07 replication fitness was examined by virus rescue experiment. Virus titer was measured by TCID_50. Error bars indicate the standard deviation of three independent experiments. The green dashed line represents the lower detection limit