Observation of the Early Structural Changes Leading to the Formation of Protein Superstructures.

Formation of superstructures in protein aggregation processes has been indicated as a general pathway for several proteins, possibly playing a role in human pathologies. There is a severe lack of knowledge on the origin of such species in terms of both mechanisms of formation and structural features. We use equine lysozyme as a model protein, and by combining spectroscopic techniques and microscopy with X-ray fiber diffraction and ab initio modeling of Small Angle X-ray Scattering data, we isolate the partially unfolded state from which one of these superstructures (i.e., particulate) originates. We reveal the low-resolution structure of the unfolded state and its mechanism of formation, hi…