Figure 2.

Structural analysis of Cd²⁺-complexed C2B. (A) Backbone superposition of four C2B structures: Cd²⁺-complexed (this work, 5T0S, orange), apo penta-mutant (5CCJ,⁴⁶ blue), Ca²⁺-complexed (1TJX,⁴⁷ cyan), and Sr²⁺-complexed (1TJM,⁴⁷ tan). (B, C) Pairwise comparison of loop regions of Cd²⁺-complexed C2B with those of the apo and Ca²⁺-complexed C2B highlights the differences between the conformation of loops and coordinating residues. The structural elements of apo and Ca²⁺-complexed C2B are shown with transparent representation. Only one Ca²⁺ ion and protein ligands of Cd²⁺ are shown for clarity in (C). (D) Coordination geometry of the Cd²⁺ site. Cd²⁺ has 7 oxygens ligands in its first coordination sphere, 6 contributed by C2B and 1 by a water molecule.