Fig. 4.

Mechanisms of Zn²⁺ ion transfer between metal carriers and Zn²⁺-dependent enzymes. a Equilibrium transfer mechanism. The Zn²⁺ ion of the donor protein (green) dissociates and enters the free Zn²⁺ pool, followed by the binding of the free Zn²⁺ ion by the acceptor protein (red). b Shared ligand mechanism. Protein–protein interactions between the donor (green) and acceptor (yellow) proteins exposes binding site residues of the acceptor protein, which coordinate to the Zn²⁺ ion to form an intermediate in which the Zn²⁺ ion is shared by the two proteins. Disengagement of the protein complex causes the Zn²⁺ ion to remain with the acceptor protein after the proteins dissociate. c Altered affinities mechanism. Protein–protein interactions between the donor (green) and acceptor (red) proteins induce conformational changes that reduce the affinity of the donor protein for the Zn²⁺ ion and/or enhance the affinity of the acceptor. The Zn²⁺ ion dissociates from the donor and is then bound by the acceptor protein. Created with BioRender.com. (Color figure online)