Fig. 3: Comparison TcThiH with TiHydG and SaNosL.

a Multiple sequence alignment of TcThiH, HydG from Thermoanaerobacter italicus (Ti) and SaNosL primary structures. Red and white boxes indicate conserved and similar amino acids in the three proteins. TcThiH secondary structure elements are depicted on top following the same color code as in Fig. 2a. Red stars highlight residues 80, 158, 300 and 306 that are discussed in the text. b L-tyrosine (left) and L-tryptophan (right) binding mode in TcThiH (this work) and SaNosL²⁵, respectively. Except for the [Fe₄S₄] cluster depicted in the ball-and-stick form, the rest of the active site and the substrate are represented as sticks and water molecules are indicated as red spheres. C, N, O, S and Fe atoms are represented in light gray (dark gray for the substrates), blue, red, yellow and brown, respectively. c The cavity maps, contoured with an accessible probe radius of 1 Å, were calculated using the X-ray models of TcThiH (left, steel blue), TiHydG³⁵ (center, ruby-red) and SaNosL (right, olive color). When present in the structural model, 5´-dA, the L-methionine bound to the [Fe₄S₄] cluster and the substrate were removed for the cavity calculation. Key residues and the [Fe₄S₄] are represented as in (b). Stereoviews of (b, c), are presented in Supplementary Figs. 11, 12, respectively.