Comparison of PA-IIL lectin from Pseudomonas aeruginosa with its homolog RS-IIL lectin from Ralstonia solanacearum. A) Alignment of amino acid sequences of PA-IIL and RS-IIL. The differing amino acids are in yellow with blue background, the amino acids participating in saccharide binding are marked by triangles, and amino acids participating in calcium coordination are marked by stars. B) Graphical representation of the overall structure of PA-IIL tetramer (ribbon) complexed with L-fucose (sticks) and calcium ions (cpk). PDB code 1UZV . C) Superposition of binding sites of RS-IIL/Me-α-Man (structure 1UQX ) and PA-IIL/Man (mannose moiety of the trimannose in structure 1OVS ) with crucial amino acids highlighted. In PA-IIL, the hydroxyl group of Ser22 makes the hydrogen bond with Asp96 and O6 of mannose interacts with Ser23. In RS-IIL, Asp96 makes directly hydrogen bond with of O6 of methyl mannoside.