Download MendeleyStructure-guided identification of function: role ofCapsicum annuumvicilin during oxidative stress.
Shikhi, M., Nair, D.T., Salunke, D.M.(2018) Biochem J 475: 3057-3071
- PubMed: 30181145
- DOI: https://doi.org/10.1042/BCJ20180520
- Primary Citation of Related Structures:
5YJS - PubMed Abstract:
Proteins belonging to cupin superfamily are known to have critical and diverse physiological functions. However, 7S globulins family, which is also a part of cupin superfamily, were undermined as only seed storage proteins. Structure determination of native protein - Vic_CAPAN from Capsicum annuum - was carried out, and its physiological functions were explored after purifying the protein by ammonium sulfate precipitation followed by size exclusion chromatography. The crystal structure of vicilin determined at 2.16 Å resolution revealed two monomers per asymmetric unit which are juxtaposed orthogonal with each other. Vic_CAPAN consists predominately of β-sheets that folds to form a β-barrel structure commonly called cupin fold. Each monomer of Vic_CAPAN consists of two cupin fold domains, N-terminal and C-terminal, which accommodate two different ligands. A bound ligand was identified at the C-terminal cupin fold in the site presumably conserved for metabolites in the crystal structure. The ligand was confirmed to be salicylic acid through mass spectrometric analysis. A copper-binding site was further observed near the conserved ligand-binding pocket, suggesting possible superoxide dismutase activity of Vic_CAPAN which was subsequently confirmed biochemically. Vicilins from other sources did not exhibit this activity indicating functional specificity of Vic_CAPAN. Discovery of bound salicylic acid, which is a known regulator of antioxidant pathway, and revelation of superoxide dismutase activity suggest that Vic_CAPAN has an important role during oxidative stress. As salicylic acid changes the redox state of cell, it may act as a downstream signal for various pathways involved in plant biotic and abiotic stress rescue.
Organizational Affiliation:
Regional Centre for Biotechnology, Structural Biology Lab, Faridabad 121001, India.
