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CH−π “T-Shape” Interaction with Histidine Explains Binding of Aromatic Galactosides to Pseudomonas aeruginosa Lectin LecA

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journal contribution
posted on 16.12.2015, 23:35 by Rameshwar U. Kadam, Divita Garg, Julian Schwartz, Ricardo Visini, Michael Sattler, Achim Stocker, Tamis Darbre, Jean-Louis Reymond
The galactose specific lectin LecA mediates biofilm formation in the opportunistic pathogen P. aeruginosa. The interaction between LecA and aromatic β-galactoside biofilm inhibitors involves an intermolecular CH−π T-shape interaction between C­(ε1)–H of residue His50 in LecA and the aromatic ring of the galactoside aglycone. The generality of this interaction was tested in a diverse family of β-galactosides. LecA binding to aromatic β-galactosides (KD ∼ 8 μM) was consistently stronger than to aliphatic β-galactosides (KD ∼ 36 μM). The CH−π interaction was observed in the X-ray crystal structures of six different LecA complexes, with shorter than the van der Waals distances indicating productive binding. Related XH/cation/π–π interactions involving other residues were identified in complexes of aromatic glycosides with a variety of carbohydrate binding proteins such as concanavalin A. Exploiting such interactions might be generally useful in drug design against these targets.