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Megadalton-sized dityrosine aggregates of α-synuclein retain high degrees of structural disorder and internal dynamics.

By Silvia Verzini, Maliah Shah, Francois-Xavier Theillet, Adam Belsom, Jan Bieschke, Erich E. Wanker, Juri Rappsilber, Andres Binolfi, Philipp Selenko

Posted 26 Jul 2020
bioRxiv DOI: 10.1101/2020.07.26.202358 (published DOI: 10.1016/j.jmb.2020.10.023)

Heterogeneous aggregates of the human protein α-synuclein (αSyn) are abundantly found in Lewy body inclusions of Parkinson′s disease patients. While structural information on classical αSyn amyloid fibrils is available, little is known about the conformational properties of disease-relevant, non-canonical aggregates. Here, we analyze the structural and dynamic properties of megadalton-sized dityrosine adducts of αSyn that form in the presence of reactive oxygen species and cytochrome c, a proapoptotic peroxidase that is released from mitochondria during sustained oxidative stress. In contrast to canonical cross-β amyloids, these aggregates retain high degrees of internal dynamics, which enables their characterization by solution-state NMR spectroscopy. We find that intermolecular dityrosine crosslinks restrict αSyn motions only locally whereas large segments of concatenated molecules remain flexible and disordered. Indistinguishable aggregates form in crowded in vitro solutions and in complex environments of mammalian cell lysates, where relative amounts of free reactive oxygen species rather than cytochrome c are rate limiting. We further establish that dityrosine adducts inhibit classical amyloid formation by maintaining αSyn in its monomeric form and that they are non-cytotoxic despite retaining basic membrane-binding properties. Our results suggest that oxidative oxidative αSyn aggregation scavenges cytochrome c′s activity into the formation of amorphous, high molecular-weight structures that may contribute to aggregate diversity in Lewy body deposits. ### Competing Interest Statement The authors have declared no competing interest.

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