Fig. 1

The crystallographic structure of Zn²⁺/Ca²⁺-bound hS100A8. a Anomalous difference Fourier maps calculated using phases and weight from the best refined atomic model (without ions) obtained with the native dataset (crystal form 1) and anomalous differences from the datasets collected at wavelengths of 1.27 Å (cyan mesh, contour at 3.5 σ) and 1.30 Å (red mesh, contour at 3.5 σ). The final model displayed as cartoon in beige and purple is superimposed for comparison. The anomalous signal clearly disappears for the wavelength above the Zn maximal absorbance peak (λ = 1.30 Å) as judged by the fact that almost no density is visible for the second anomalous difference Fourier map (red mesh). b Overview of the structure of Zn²⁺/Ca²⁺-bound hS100A8 derived from crystal form 1 at 2.2 Å resolution showing two zinc bound at the homodimer interface (yellow spheres). The four calcium ions are displayed as green spheres. c Close-up view on the Zn²⁺-binding site revealing an all-His binding motif formed by two residues from each monomer. d In two out of eight molecules within the asymmetric unit, His27 from monomer A is replaced by a chloride ion (gray sphere)