Function, Structure, and Transport Aspects of ZIP and ZnT Zinc Transporters in Immune Cells

Figure 2

Overview of ZnT. (a) Topological model of ZnT. TMDs of ZnT are divided into two groups; TM1, 2, 4, and 5 form one bundle and TM3 and 6 form the other bundle. TM2 and TM4 share the Zn²⁺ binding site via HXXXD motifs. TM3 and 6 trigger the charge interlock that stabilizes the dimeric conformation. (b) Transport mechanism. ZnT has two major conformations, the inward-open and outward-open conformations, similar to ZIP. CTDs contain 4 Zn²⁺ that are not transported across the lipid bilayer but contribute to the stabilization of dimerization in a zinc-dependent manner. In the YiiP crystal structure, one Zn²⁺ is found in the link between the TMD and CTD (pink circle).

(a)

(b)