FIGURE 2.

Overall structure of S-TIM5-dCD. A, superposition of the in crystallo hexameric forms (carried out in Coot). For clarity, every second protomer is shaded gray (S-TIM5-A in purple, S-TIM5-T in red, and S-TIM5-C in cyan). Blue arrowheads highlight interfaces between protomers. Inset, close-up of the middle region of the hexamer highlighting the greater compactness of the unbound S-TIM5-A structure (opposite protomers in the hexamer are ∼2.5 Å closer) as compared with the ligand-bound structures of S-TIM5-C and S-TIM5-T. B, superposition of the monomers from each structure. Zn²⁺ ions are displayed as spheres. C, secondary zinc binding motif in the S-TIM5-C (cyan) is substituted with a disulfide bond (represented by Cys²² and Cys⁵⁴ as sticks). Secondary zinc (Zn”, orange sphere) and its binding residues (orange lines, His⁹⁴ is labeled) from the structurally aligned T4 bacteriophage dCD (PDB code 1VQ2) are shown. Catalytic zinc ions are represented as overlapped cyan and orange spheres for S-TIM5-C and 1VQ2, respectively.