Abstact

Plant seed storage proteins (SSPs) serve as a nutrient source and are suggested to be crucial for seed survival during dormancy and desiccation. They form highly stable and environmentally stress-resistant amyloid structures. SSP amyloids are gaining significant attention for fabricating sustainable biomaterials in recent times; however, the requirement for optimized fibrillation conditions limits their practical use. Therefore, understanding the molecular mechanism of SSP amyloidogenesis, biochemical conditions, and the biophysical properties of the resultant amyloid fibrils becomes crucial. This study investigates the amyloidogenic properties of Cruciferin-3 (CRU-3), a major SSP from Arabidopsis thaliana, focusing on the 12-residue representative peptide, L(223)-Y(234) (LY12), computationally predicted to be amyloidogenic. LY12 forms beta-sheet rich amyloid fibrils in a nucleation-dependent manner in vitro with the potential to seed self-aggregation. The peptide fibrillation was found to be pH-dependent and showed a moderate resistance to Proteinase K treatment. Molecular-level insight into the structure of LY12 fibrils was obtained using cryogenic-electron microscopy (cryo-EM) at a high resolution of 2.86 A. The structure of LY12 fibrils revealed a C2 symmetrical, left-handed, twisted core comprising three non-equivalent peptide stacks. This unique cross beta-sheet dense core, stabilized by hydrophobic and electrostatic interactions, and surrounded by low-density peptide layers, distinguishes them from pathological amyloids. This study explores the conditions for LY12 amyloid formation and deciphers their biophysical attributes and structural details, suggesting the potential physiological roles and biomaterial applications of CRU-3 amyloids.