Fig. 3: X-ray structure of P40/P90 and of its complex with oligosaccharide 3SL.

a Ribbon representation, with three 90° apart views, of the crystal structure from the P40/P90 N-terminal domain that is organized, similarly to P1, around a seven-blade β-propeller (light orange) from where it emerges the crown (pink). The sialic binding site found in P40/P90 is explicitly indicated. The predicted C-terminal domain of P40/P90 is also shown (cyan), modeled from the C-terminal domain of the orthologous adhesin P110 from M. genitalium. b Topology of the β-propeller from P40/P90. Loops contributing to the crown are colored pink. The first blade β-sheet contains only three strands in P40/P90 placing the N-end at the propeller face opposite to the one in P1. Localizations of the disordered loops and sialic binding site are indicated with black dots (black) and a star (blue), respectively. The position of the cleavage site, which results in the corresponding P40 and P90 separate polypeptides, is depicted with a pentagram (pale blue). Strands and loops are not in scale. c Binding of 3SL to the N-terminal domain of P40/P90. Ribbon representation of the P40/P90N structure in complex with oligosaccharide 3SL. The inset shows a detail of the residues shaping the binding pocket. The electron density omit map (at 0.9 sigma) corresponding to 3SL is also shown.