Fig. 7. Crystal structures of LecB_PA14 in complex with 2 (A), 11 (B) and 12 (C). (Upper panel) Display of electron density for the ligands at 1σ. Ca²⁺-ions are shown as green spheres. ((A) lower panel) Methyl α-l-fucoside (2) establishes a lipophilic interaction with T45 and A23. The crystal structure reveals a water-mediated hydrogen bond between the anomeric oxygen and S97 and an additional hydrophobic interaction of the aglycon with A23. ((B) lower panel) The crystal structure with α-1,3-d-mannosyl d-mannose (11) indicates one water mediated hydrogen bond between the 6-OH group and S97, as well as an interaction of the same water with the 2-OH group of the second mannose. An additional lipophilic contact between the aglycon and A23 is observed. ((C) lower panel) The tetrasaccharide Lewis^a (12) establishes water-mediated hydrogen bonds via two water molecules and lipophilic contacts with T45 and A23. The C-terminus of each chain involved in the CRD of the neighboring chain is shown as cartoon in green. Ca²⁺-ions are shown as green spheres.