Fig. 1: Overview of MtSerB2 structural features based on homology modelling.

a MtSerB2 homology model (bottom) constructed on the basis of MaSerB crystal structure¹⁴ (top, 83.7% sequence identity). The two predicted monomer chains are respectively depicted in grey and in colour. Structural regions of interest are highlighted: C-terminal C1 cap module (purple), Rossmannoid fold (green), N-terminal ACT domains (yellow and red). The predicted magnesium ions cofactors are represented as pink spheres inside the Rossmannoid fold of each monomer chain. The two monomer chains are related by C2 symmetry and exchange their ACT1 domain to form a dimer with the ACT2 domain of the other monomer chain (c). b Predicted conformation of the 12 residues-long hinge region separating ACT2 and ACT1 domains, and allowing ACT1 domain-swapping in MtSerB2 homology model. c Intermolecular dimeric arrangement of ACT1 and ACT2 domains in MtSerB2 homology model. The ACT dimer exhibits an eight-stranded antiparallel beta-sheet in the order 4–1–3–2–2–3–1–4 on one side and four helices in the order 2–1–1–2 on the other. One monomer chain is depicted in grey and the other in yellow. d The archetypical dimeric ACT domain arrangement of E. coli phosphoglycerate dehydrogenase tetramer⁸⁵ (PDB: 1PSD) with two l-Ser molecules bound at the interface.