Poster Presentation 2014 International Biophysics Congress

 Effect of glycosidic linkage on the sugar specificity of Jacalin (#265)

Abhinav K.V. 1 , Kaushal Kishor Sharma 1 , Padmanabh Mishra 1 , Avadesha Surolia 1 , Mamannamana Vijayan 1
  1. Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India

 Earlier structure analyses of the β-prism I fold lectin called jacalin in this laboratory1  led to a complete characterization of the extended binding site of the lectin involving a primary binding site, where all the hydrogen bonds occur, an aromatic secondary binding site A and a secondary binding site B where most of the interactions are through water bridges2 3 . At the monosaccharide level, the anomeric oxygen of the bound galactose points towards the secondary binding site A. The structures presently analysed include a complex of jacalin with methyl-β-galactopyranoside (the α-derivative has already been analysed earlier) and those involving α and β substitution of aromatic groups at the sugar. The lower affinity resulting from β-substitution appears to have been caused by subtle variations including perhaps the distortion of the sugar ring. Aromatic substituents show higher affinity presumably on account of aromatic interactions with the secondary site A. Structures of a total of 5 disaccharide-jacalin complexes (three β(1-3) linked and two α-linked (α(1-3) and α(1-4)) have also been determined and the sugar occupancy is in consonance with earlier observations4 5 , that the reducing end occupies the primary binding site when the linkage is β(1-3) with the non-reducing end oriented towards secondary binding site B, while in an α-linked disaccharide, the non-reducing sugar occupies the primary binding site with the non-reducing end oriented towards secondary binding site A . These observations are under further examination for their full implications.

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  4. Sharma, A. and Vijayan, M. (2011). Glycobiology. 21(1), 23-33.
  5. Chandran, T., Sharma, A. and Vijayan, M. (2013). Adv Protein Chem Struct Biol. 92,135-78.