Nanomolar inhibitor of the galectin-8 N-terminal domain binds via a non-canonical cation-π interactionPurić, Edvin (Avtor) Hassan, Mujtaba (Avtor) Sjövall, Fredrik (Avtor) Tomašič, Tihomir (Avtor) Pevec, Mojca (Avtor) Lah, Jurij (Avtor) Adrover Forteza, Jaume (Avtor) Sundin, Anders (Avtor) Leffler, Hakon (Avtor) Nilsson, Ulf (Avtor) Logan, Derek T. (Avtor) Anderluh, Marko (Avtor) carbohydrateslead optimizationstructure-based drug designX-ray crystallographyGalectin-8 is a tandem-repeat galectin consisting of two distinct carbohydrate recognition domains and is a potential drug target. We have developed a library of galectin-8N inhibitors that exhibit high nanomolar Kd values as determined by a competitive fluorescence polarization assay. A detailed thermodynamic analysis of the binding of d-galactosides to galectin-8N by isothermal titration calorimetry reveals important differences in enthalpic and/or entropic contributions to binding. Contrary to expectations, the binding of 2-O-propargyl-d-galactoside was found to strongly increase the binding enthalpy, whereas the binding of 2-O-carboxymethylene-d-galactoside was surprisingly less enthalpy-driven. The results of our work suggest that the ethynyl group can successfully replace the carboxylate group when targeting the water-exposed guanidine moiety of a critical arginine residue. This results in only a minor loss of affinity and an adjusted enthalpic contribution to the overall binding due to non-canonical cation-π interactions, as evidenced by the obtained crystal structure of 2-O-propargyl-d-galactoside in complex with the N-terminal domain of galectin-8. Such an interaction has neither been identified nor discussed to date in a small-molecule ligand-protein complex.20252025-03-17 11:19:08Članek v reviji167856UDK: 615.4:54ISSN pri članku: 2399-3669DOI: 10.1038/s42004-025-01458-6COBISS_ID: 229077763sl