Investigation of structural and saccharide binding transitions of Bauhinia purpurea and Wisteria floribunda lectins

Two novel medicinally important legume lectins from Bauhinia purpurea (BPL) and Wisteria floribunda (WFL) possessing extended sugar binding site were investigated for functional and conformational transitions using biochemical and biophysical techniques as well as bioinformatical tools. Homology model of BPL was constructed using the Schrodinger suite and docked with N-acetyl galactosamine and T-antigen disaccharide (Galβ1-3GalNAcαO-Me). The longer loop D in the structure of WFL compared to that in BPL was found to be responsible for its specificity to LacdiNac (β-D-GalNAc-[1 → 4]-DGlcNAc) over Galβ1-3GalNAc. BPL remained functionally stable up to 40 °C whereas WFL remained stable upto 70 °C indicating the strength of the sugar binding site geometry. Both the lectins showed intense but non-specific secondary structure in the range of 65–90 °C. WFL showed rapid aggregation above 80 °C as indicated by light scattering intensity. The lectins showed simultaneous dissociation and multistate unfolding in the vicinity of GdnHCl. At pH 1.0, both the lectins exhibited molten globule like structures, which were characterized further and were found to respond in a different way towards denaturants. The results have provided valuable insights into the molecular basis of the activity and stability of the two lectins. •Saccharide binding and structural transitions of Bauhinia and Wisteria lectins.•Homology model and docking of Bauhinia lectin.•Structural elements responsible for different disaccharide specificity.•Unique thermal transitions of the lectins.•Characterization of acid induced molten globule like species.