Fig. 4.

Zn²⁺-dependent dimerization of Brpt1.5. Zn²⁺-dependent dimers with similar architecture are seen in all crystals. Zn²⁺ ions are shown as red spheres, and protomers are shown in cartoon representation. Zn²⁺-coordinating residues are schematized to the right of the respective structures. (A) SeMet-labeled quadruple mutant (dark red and pink). (B) Native1 (dark and light violet) (diffraction data were isomorphous with the SeMet data set). (C) Native2 (dark and light green) crystallizes with differing unit cell dimensions, and subtle differences are observed in domain placement. (D and E) Two distinct symmetric dimers are formed by the two chains present in the non–Se-labeled quadruple mutant (chain A, blue; chain B, cyan), with differences in domain placement.