Fig. 3: Crystal structure of ThC.

A Ribbon diagram of the nThC monomer colored according to the sequence in blue at the N-terminus to red at the C-terminus. The disulfide bond between Cys3 and Cys111 is shown as a magenta ball. B Dimer structure of rThC in complex with Ca²⁺ (green ball) and fucose (ball-and-stick model, yellow: carbon, red: oxygen). C A close-up view of the fucose-binding site of rThC. The bound Ca²⁺ ions and fucose are shown as green balls and stick models, respectively. Residues are colored according to the chain as in (B). A Fo-Fc map of fucose and Ca²⁺ contoured at 3.0 σ is shown. D Pseudodomain swapping structure in dimeric rThC. Gly 131*, shown in orange, of one protomer intervenes in the other. E Structural comparison of the Ca²⁺-binding configuration between wild type (left) and Q25K (right). A close-up view of the fucose-binding site is shown. Individual protomers are shown in red and blue. The substituted residues (Q25 and K25) are shown in green.