Fig. 4: RSV-F^L305I mutation alters the structure and function of the palivizumab binding site.

a Space filling structural model of the RSV-F trimer with antigenic sites Ø (orange), II (green), and IV (purple) highlighted. b Superimposition of the residues at position 305 in RSV-F L305 (green) and RSV-F I305 (peach). The ___location of the leucine and isoleucine residues at position 305 are indicated in blue and red respectively. c Computational model of the changes in the PZMB binding site (site II) with the L305I mutation. Conformational changes in select amino acid residues surrounding position 305 are indicated. d EC₅₀ curves of PZMB neutralization of RSV WT (blue) and RSV L305I (red) determined by flow cytometry (n = 3). EC₅₀ values are indicated in parentheses. Data were fit using a non-linear regression curve and EC₅₀ values were compared using the extra sum-of-squares F test. e Total protein and anti-histidine-stained gels of purified DS-Cav1^L305 and DS-Cav1^I305 constructs. f, g SPR binding curves of PZMB to DS-Cav1^L305 and DS-Cav1^I305 are indicated in blue and red respectively (n = 2). Fitted curves were determined using a 1:1 binding model and are indicated in black. Observed K_D values are indicated for each curve.