Vicilin, a chitin binding protein from Sesbania grandiflora: Structural insights and functional potential as an antifungal agent

Sesbania grandiflora, a fast-growing shrub from the Fabaceae family, is extensively researched for its therapeutic properties. Despite its highly valued medicinal properties, there have been no reports on exploring the proteome of Sesbania grandiflora. The present study aims to address this gap by investigating the proteomic profile of Sesbania grandiflora seeds with a primary focus on identifying storage proteins. The proteomic data disclosed an abundant vicilin protein from the seeds, which was subsequently purified to homogeneity. Structural analysis revealed the heterotrimeric nature of the purified protein, with an intact molecular weight of approximately 130 kDa and the presence of N-glycosylation. Further, in-gel digested protein bands were analyzed via LC-MS/MS, and partial de novo sequences were deduced through a homology-driven proteomic approach. Circular dichroism spectroscopy revealed that the vicilin is predominantly composed of β-sheet structures, with a melting temperature of 69.3 °C. Functional studies demonstrated the protein's chitin-binding capability via chitin affinity chromatography, highlighting its anti-mycotic properties. The antifungal activity was quantified, showing that approximately 15 μM of the purified protein inhibited 50 % of Fusarium oxysporum growth. A cell permeability assay with propidium iodide staining confirmed the interaction between the protein and the fungal cell wall, highlighting its role in antifungal activity.