Fig. 3: HDX-MS analysis shows structural stabilization in three regions of HSA lacking L585.

a–e Deuterium uptake plots for peptide segments of WT HSA (black) and L585X (red) of (a) the C-terminal peptides (i.e., with or without L585), b–d the peptide regions that showed a statistically significant difference in deuterium incorporation and (e) a peptide that showed no difference. The values were normalized to the deuterium uptake of the corresponding peptide in the “maximally labeled” control sample. The data points represent the mean ± s.d. of triplicates, except for 2960 min, where n = 1. *Marks a statistically significant change in HDX as defined in the “Methods” section. f, g The C-terminal peptide is highlighted in green, whereas the structural regions stabilized by removal of L585 are highlighted in orange (409–420), red (496–506), and dark blue (530–550) on the crystal structures of HSA (DI; pink, DII; wheat, DIII; light cyan) (f) alone and (g) in complex with hFcRn (HC; light green, β₂m; gray). The regions that were not covered in the HDX data are colored in black. The figures were made using PyMOL with the crystallographic data of HSA (PDB ID 1AO6) and the WT HSA-hFcRn co-complex (PDB ID 4N0F)²⁶.