Biometals as conformational modulators of ?-synuclein photochemical crosslinking.

ABSTRACT: Metal dyshomeostasis has long been linked to Parkinson's disease (PD), and the amyloidogenic protein ?-synuclein (?S) is universally recognized as a key player in PD pathology. Structural consequences upon coordination of copper and iron to ?S have gained attention due to significant dyshomeostasis of both metals in the PD brain. Protein-metal association can navigate protein folding in distinctive pathways based on the identity of the bio-metal in question. In this work, we employed photo-chemical crosslinking of unmodified proteins (PICUP) to evaluate these potential metal ion-induced structural alterations in the folding dynamics of N-terminally acetylated ?S (^NAc?S) following metal coordination. Through fluorescence analysis and immunoblotting analyses following photoirradiation, we discovered that coordination of iron obstructs copper-promoted crosslinking. The absence of intra-molecular crosslinking upon iron association further supports its C-terminal coordination site and suggests a potential role for iron in mitigating nearby post-translational modification of tyrosine residues. Decreased fluorescence emission upon synergistic coordination of both copper and iron highlighted that although copper acts as a conformational promotor of ^NAc?S crosslinking, iron inhibits analogous conformational changes within the protein. The metal coordination preferences of ^NAc?S suggest that both competitive binding sites as well as dual metal coordination contribute to the changes in folding dynamics, unveiling unique structural orientations for ^NAc?S that have a direct and measureable influence on photoinitiated dityrosine crosslinks. Moreover, our findings have physiological implications in that iron overload, as is associated with PD-insulted brain tissue, may serve as a conformational block of copper-promoted protein oxidation.

SUBMITTER: Abeyawardhane DL 

PROVIDER: S-EPMC7334974 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature