In this diagram of the ZnT-8 R325W variant, the loop domain linking β2 to α2 at the outer edge of the C-terminal domain intracellular part faces the viewer. Note that Trp325 points away from the interface with the other monomer. The bacterial structure is indicated in green, the human structure in yellow, and the other monomer in blue. The four front spheres at the interface of the intracellular domains represent the positioning of the two binuclear zinc ion clusters in sites Z3 and Z4 in each of the protomers, and the faint back spheres the zinc ion in site Z2 in each of the protomers. The side-chains of Trp325, Asp326, and Asp295 are presented by a "ribbon structure".