title: Structural-functional insights and studies on saccharide binding of Sophora japonica seed lectin.
abstract: Functional and conformational transitions of the Sophora japonica seed lectin (SJL) were studied in detail using bioinformatics and biophysical tools. Homology model of the lectin displayed all the characteristics of the legume lectin monomer and the experimental observations correlated well with the structural information. In silico studies were performed by protein-ligand docking, calculating the respective binding energies and the residues involved in the interactions were derived from LigPlot(+) analysis. Fluorescence titrations showed three times higher affinity of T-antigen disaccharide than N-acetyl galactosamine (GalNAc) towards SJL indicating extended sugar binding site of the lectin. Thermodynamic parameters of T-antigen binding to SJL indicated the process to be endothermic and entropically driven while those of GalNAc showed biphasic process. SDS-PAGE showed post-translationally modified homotetrameric species of the lectin under native conditions. In presence of guanidine hydrochloride (0.5-5.0M), the tetramer first dissociated into dimers followed by unfolding of the protein as indicated by size exclusion chromatography, fluorescence and CD spectroscopy. Different structural rearrangements were observed during thermal denaturation of SJL at physiological pH 7.2, native pH 8.5 and molten globule inducing pH 1.0. Topological information revealed by solute quenching studies at respective pH indicated differential hydrophobic environment and charge density around tryptophan residues.
authors.affiliation: Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
authors.forename: Priya
authors.initials: P
authors.lastname: Yadav
authors.affiliation: Division of Physical and Materials Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Shahane
authors.affiliation: Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
authors.forename: Sureshkumar
authors.initials: S
authors.lastname: Ramasamy
authors.affiliation: Division of Physical and Materials Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
authors.forename: Durba
authors.initials: D
authors.lastname: Sengupta
authors.affiliation: Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India. Electronic address: sm.gaikwad@ncl.res.in.
authors.forename: Sushama
authors.initials: S
authors.lastname: Gaikwad
mesh_terms: D000116:Acetylgalactosamine / Q000378:metabolism; D000957:Antigens, Viral, Tumor / Q000378:metabolism; D050260:Carbohydrate Metabolism; D006863:Hydrogen-Ion Concentration; D062105:Molecular Docking Simulation; D037121:Plant Lectins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D000957:Antigens, Viral, Tumor; D037121:Plant Lectins; C104735:SJAsg agglutinin, Sophora japonica; D000116:Acetylgalactosamine
keywords: Dissociation; Docking; Homology model; Ligand binding; Sophora japonica seed lectin; Thermal transitions