Molecular Characterization of Mannose Binding Lectins

Abstract

Lectins are proteins of non-immunologic origin that bind to carbohydrates with high fidelity. They constitute a large class of multivalent recognition molecules that specifically interact with their cognate sugar moieties for decoding the information displayed. Protein-carbohydrate interactions play a pivotal role in mediating biomolecular recognition. We attempt to unravel its intricacies by understanding how the glycan code is interpreted by a myriad of carbohydrate binding proteins. This thesis entitled ―Molecular characterization of Mannose binding lectins‖ presents a study on this class of proteins which are known to be mannose specific from the two kingdoms of life – Mammalian ER Cargo Lectins, having the Legume lectin fold and Horcolin, a plant lectin, having β-prism I fold. Although the proteins have a distinct role, they share a common ligand specificity at the monosaccharide level that is they are Mannose Binding Proteins (MBP). Pattern recognition through heatmaps assists in reducing data complexity and enhances data interpretation by visualization. Hence, we have exploited it in this study to analyze the data generated from amino acid variability in a set of 46 legume lectins. Our findings on sequence-based variability and phylogenetic analysis are complementary to the previous studies, revealing that legume lectins arose from divergent evolution while retaining a common β sandwich fold. There is a clear distinction in the sequence identity among these proteins specific to a particular monosaccharide. The results from percentage composition justify the plausible role of certain amino acid residues in the carbohydrate binding site for non-covalent interactions with the sugar thereby imparting specificity.