Fig. 1.

Surface metal ion–binding site in S10A. 2Fo−Fc electron density map surrounding the metal ion–binding site in S10A are contoured at the 1.0-σ level in gray color. The residues of S10A are shown as a green-stick model, and oxygen and nitrogen atoms are shown in red and blue, respectively. Water molecules are illustrated as red-sphere models. Ca²⁺ and Zn²⁺ ions are shown as green- and orange-sphere models, respectively. His98 in the crystal symmetric subunit is shown in marine color and labeled in red. Hydrogen bonds are shown as dashed lines. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)