Parkinson’s disease (PD) is the second most common neurological disease and belongs to a group of neurodegenerative disorders called synucleinopathies in which pathological aggregates of N-terminally acetylated α-synuclein (NAcα-Syn) accumulate in various regions of the brain. In PD, these NAcα-Syn aggregates have been found to contain covalent dityrosine crosslinks, which can occur either intermolecularly or intramolecularly. Cerebral metal imbalance is also a hallmark of PD, warranting investigations into the effects of brain biometals on NAcα-Syn. NAcα-Syn is an intrinsically disordered protein, and metal-mediated conformational modifications of this structurally dynamic protein have been demonstrated to influence its propensity for dityrosine formation. In this study, a library of tyrosine-to-phenylalanine (Y-to-F) NAcα-Syn constructs were designed in order to elucidate the nature and the precise residues involved in dityrosine crosslinking of Fe-bound NAcα-Syn. The structural capacity of each mutant to form dityrosine crosslinks was assessed using Photo-Induced Cross-Linking of Unmodified Proteins (PICUP), demonstrating that coordination of either FeIII or FeII to NAcα-Syn inhibits dityrosine crosslinking among the C-terminal residues. We further demonstrate that Y39 is the main contributor to dityrosine formation of Fe-bound NAcα-Syn, while Y125 is the main residue involved in dityrosine crosslinks in unmetalated NAcα-Syn. Our results confirm that iron coordination has a global effect on NAcα-Syn structure and reactivity.

The interferon response suppression by the respiratory syncytial virus relies on two unique non-structural proteins, NS1 and NS2, that interact with cellular partners through high order complexes. We hypothesized that two conserved proline residues, P81 and P67, participate in the conformational change leading to oligomerization. We found that molecular dynamics of NS1 show a highly mobile C-terminal helix, which become rigid upon in silico replacement of P81. A soluble oligomerization pathway into regular spherical structures at low ionic strength competes with an aggregation pathway at high ionic strength upon temperature increase. P81A requires higher temperatures to oligomerize and has a small positive effect on aggregation, while P67A is largely prone to aggregation. Chemical denaturation shows a first transition, involving a large fluorescence and ellipticity change corresponding to both a conformational change and substantial effects on the environment of its single tryptophan, that is strongly destabilized in P67A but stabilized by P81A. The subsequent global cooperative unfolding corresponding to the main ß-sheet core is not affected by the proline mutations. Thus, a clear link exists between the effect of P81 and P67 on the stability of the first transition and oligomerization/aggregation. Interestingly, both P67 and P81 are located