Fig. 2: Crystal structure of TcThiH.

a Overall structure of ThiH where the radical SAM core is depicted in indian red (β-strands) and blue (α-helices). The N- and C-terminal stretches are depicted in gold and green, respectively. The CX₃CX₂C-motif containing loop and the additional β-sheet are represented in purple. The [Fe₄S₄]-cluster is depicted in ball-and-stick while 5´-dA, the L-methionine bound to the [Fe₄S₄] cluster and L-tyrosine are represented as sticks. C, N, O, S and Fe atoms are represented in light gray (dark gray for L-tyrosine), blue, red, yellow and brown, respectively. b Zoom of the L-tyrosine TcThiH binding site. The Fo − Fc difference Fourier (omit) electron density map for 5´-dA, L-methionine and L-tyrosine is contoured at 4.5 σ and depicted as green mesh (cover radius 2.0 Å). Atoms are represented and colored as in (a). c Substrate (L-tyrosine) binding mode at the TcThiH active site. Atoms are represented and colored as in (a). The 2Fo − Fc electron density map of L-tyrosine, that is not shown here to visualize the substrate’s interactions with the protein, can be found in Supplementary Fig. 4a. d Scheme of interactions between the L-tyrosine and the TcThiH active site; Distances in Å (X-ray model, molecule A), between the heavy atoms of the protein and those of the substrate, are indicated at the protein atoms for clarity. The atomic coordinate errors have been estimated to 0.036 Å for all the L-tyrosine heavy atoms (0.046 Å for the overall structure) using the Online_DPI server⁵⁶. e Zoom of the substrate-free TcThiH active site in the same orientation as in (b) (see main text). The Fo − Fc difference Fourier (omit) electron density map surrounding the sulfate ion and the water molecules is contoured at 3 σ and depicted as green mesh (cover radius 2.0 Å). f Substrate-free TcThiH active site in the same orientation as in (c). Stereoviews of (b, c, e, f) are depicted in Supplementary Figs. 4b, 5, 6 and 7, respectively.