Exploring Glycan Binding Specificity of Odorranalectin by Alanine Scanning Library.

Fluorescently labelled alanine scan analogues of odorranalectin (OL), a cyclic peptide that exhibits lectin like properties, were screened for binding BSA-conjugated monosaccharides using an enzyme-linked lectin assay (ELLA). Results revealed that Lys, Phe, Tyr, Gly, Leu, and Thr were crucial for binding BSA-L-fucose, BSA-D-galactose and BSA--acetyl-D-galactosamine. Notably, Ala substitution of Ser, Pro, and Val resulted in higher binding affinities compared to the native OL. The obtained data also indicated that Arg plays an important role in differentiation of binding for BSA-L-fucose/D-galactose from BSA--acetyl-D-galactosamine. The thermodynamics of binding of the selected alanine analogues was evaluated by isothermal titration calorimetry. Low to moderate binding affinities were determined for the tetravalent MUC1 glycopeptide and asialofetuin, respectively, and high for the fucose rich polysaccharide, fucoidan. The thermodynamic profile of interactions with asialofetuin exhibits shift to an entropy-driven mechanism compared to the fucoidan, which displayed an enthalpyentropy compensation, typically associated with the carbohydratelectin recognition process.