Fig. 1: Structures of Bt1762-63 in the presence of β2,6 FOS.
From: Insights into SusCD-mediated glycan import by a prominent gut symbiont
a, b Schematic overview of the B. theta levan Sus apparatus (a), encoded by the PUL spanning Bt1754-65 (b). NTE is the N-terminal extension of Bt1763. Bt1759 and Bt1765 are periplasmic GH32 β-fructosidases, Bt1757 is a predicted fructokinase and Bt1758 is a predicted inner membrane (IM) major facilitator superfamily (MFS) transporter. Bt1754 is a hybrid two-component system that binds directly to fructose in the periplasm to upregulate expression of the PUL (b)19. c Cartoon representation of the Bt1762-63 dimer with bound FOS molecules shown as stick models, with oxygens coloured red and carbons yellow. Bt1762 (SusD) is coloured green and Bt1763 (SusC) cyan. The plug domain of Bt1763 is coloured purple. d Close-up cut-away view of the two FOS molecules inside one of the BT1762-63 monomers. e Cartoon comparisons of Bt1762-63 with shorter FOS (left; PDB ID 9ZAZ; 2.69 Å resolution), without ligand (middle panel; PDB ID 6Z8I; 2.62 Å resolution), and with longer FOS (right; PDB ID 6Z9A; 3.1 Å resolution). The bound FOS molecules are shown as space-filling models. The N-terminal hinge at the back of BT1762, allowing opening of the transporter at the front (arrow), is labelled for the complex without ligand. Crystal structure figures were made with Pymol (https://pymol.org/2/).
