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Guanidine hydrochloride denaturation of dopamine‐induced α‐synuclein oligomers: A small‐angle X‐ray scattering study
Author(s) -
Pham Chi L. L.,
Kirby Nigel,
Wood Kathleen,
Ryan Timothy,
Roberts Blaine,
Sokolova Anna,
Barnham Kevin J.,
Masters Colin L.,
Knott Robert B.,
Cappai Roberto,
Curtain Cyril C.,
Rekas Agata
Publication year - 2014
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.24332
Subject(s) - guanidine , chemistry , alpha synuclein , hydrochloride , conformational isomerism , amyloid (mycology) , dopamine , biophysics , stereochemistry , crystallography , biochemistry , molecule , organic chemistry , biology , parkinson's disease , neuroscience , medicine , inorganic chemistry , disease , pathology
Alpha‐synuclein (α‐syn) forms the amyloid‐containing Lewy bodies found in the brain in Parkinson's disease. The neurotransmitter dopamine (DA) reacts with α‐syn to form SDS‐resistant soluble, non‐amyloid, and melanin‐containing oligomers. Their toxicity is debated, as is the nature of their structure and their relation to amyloid‐forming conformers of α‐syn. The small‐angle X‐ray scattering technique in combination with modeling by the ensemble optimization method showed that the un‐reacted native protein populated three broad classes of conformer, while reaction with DA gave a restricted ensemble range suggesting that the rigid melanin molecule played an important part in their structure. We found that 6 M guanidine hydrochloride did not dissociate α‐syn DA‐reacted dimers and trimers, suggesting covalent linkages. The pathological significance of covalent association is that if they are non‐toxic, the oligomers would act as a sink for toxic excess DA and α‐syn; if toxic, their stability could enhance their toxicity. We argue it is essential, therefore, to resolve the question of whether they are toxic or not. Proteins 2014; 82:10–21. © 2013 Wiley Periodicals, Inc.