Analysis of the ¹H–¹⁵N HSQC spectra of S100A1 in complex with the unlabeled S100B.

<p>(A) Overlapped NMR HSQC spectra of ¹⁵N-S100A1 in black and ¹⁵N S100A1 complex with unlabeled S100B in a 1:1 ratio (red). Residues displaying significant intensity decreases and perturbed chemical shifts are shown by boxes (green and blue, respectively).</p> <p>(B) Bar plot presenting the changes in cross-peak chemical shift of free-form S100A1 and the S100A1-S100B complex. The blue line shows the threshold of selected residues (red) that display a notable perturbation.</p> <p>(C) Bar plot presenting the decrease in the cross-peak intensity ratio (I/I₀) of S100A1 and the S100A1-S100B complex. The threshold (blue line) of chosen residues indicates a notably reduced intensity. Selected residues are highlighted in red.</p> <p>(D) Ribbon (stick) diagram of S100A1 in green obtained using the PyMOL program. The residues that exhibit chemical shift perturbations and intensity decreases are shown in magenta.