A profile of protein-protein interaction: Crystal structure of a lectin-lectin complex

• Purification of Butea monosperma (BML) & Spatholobus parviflorus (SPL) seed lectins.
• BML-SPL binding titration by ITC, as model for thermodynamics of protein-protein interaction.
• Crystal structure of BML-SPL binary complex as models for protein-protein interaction.
• Significance of homologous protein-protein interaction as evidenced from BML-SPL interaction.

Proteins may utilize complex networks of interactions to create/proceed signaling pathways of highly adaptive responses such as programmed cell death. Direct binary interactions study of proteins may help propose models for protein-protein interaction. Towards this goal we applied a combination of thermodynamic kinetics and crystal structure analyses to elucidate the complexity and diversity in such interactions. By determining the heat change on the association of two galactose-specific legume lectins from Butea monosperma (BML) and Spatholobus parviflorus (SPL) belonging to Fabaceae family helped to compute the binding equilibrium. It was extended further by X-ray structural analysis of BML-SPL binary complex. In order to chart the proteins interacting mainly through their interfaces, identification of the nature of forces which stabilized the association of the lectin-lectin complex was examined. Comprehensive analysis of the BMLSPL complex by isothermal titration calorimetry and X-ray crystal structure threw new light on the lectin-lectin interactions suggesting of their use in diverse areas of glycobiology.

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