Fig 1.

(A). Superimposed HSQC spectra of 1.01 mM S100A9 (¹⁵N-labeled) with those of S100A12 at molar ratios of 1:0 (blue) and 1:1 (red). The residues are shown in a black box were recognized using bar diagrams. (B). Bar diagram analysis of chemical shift (¹H and ¹⁵N) perturbations of the amino acid residues in S100A12 upon complex formation with the S100A9. The threshold of selected residues exhibiting a significant change is represented by a violet line (>0.023). Following equation was used to calculated perturbation, combined shift difference = [(proton shifts)² + (nitrogen shifts/6.51)²]^0.5 (C). Bar diagram analysis of changes in cross-peak intensity ratio (I/I₀). I represents the intensity of the S100A9–S100A12 complex, and I₀ is the intensity of free S100A12. The violet line shows the threshold of selected residues that display a notably reduced intensity (<0.26). (D). Selected residues of S100A9 labeled in red on the three-dimensional structure of the heterodimer complex of S100A9 (green) and S100A12 (blue).