Characterization of alpha-synuclein interactions with selected aggregation-inhibiting small molecules.
The 140-residue protein alpha-synuclein (aS) has been implicated in the molecular chain of events leading to Parkinson's disease, which relates to the hierarchical aggregation of aS into soluble oligomers and insoluble fibrils. A number of small organic molecules have been reported to inhibit aS aggregation. Here, the interactions of chlorazole black E, Congo red, lacmoid, PcTS-Cu (2+), and rosmarinic acid with aS are examined by NMR spectroscopy to identify aS sequence elements that are masked by these compounds. Surprisingly, similar aS interaction sites, encompassing residues 3-18 and 38-51, were obtained for all molecules at equimolar small molecule:aS ratios. At higher ratios, virtually the entire amphiphilic region of aS (residues 2-92) is affected, revealing the presence of additional, lower affinity interaction sites. Upon rearranging the high-affinity interaction sites over the aS amphiphilic region in an aS mutant form, perturbations of the entire amphiphilic region were found to have already been obtained at equimolar ratios, indicating a high specificity for the original binding sites. CD spectroscopy reveals that, in the presence of the small molecules, the aS structure is still dominated by random-coil characteristics. The strongest effects are exerted by molecules that contain sulfonate groups adjacent to aromatic systems, often present in multiple copies in a symmetrical arrangement, suggesting that these elements are useful for developing an aS-specific chemical chaperone.
Rao
Jampani Nageswara
JN
Department of Biochemistry and Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA.
Dua
Varun
V
Ulmer
Tobias S
TS
D002942:Circular Dichroism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D051844:alpha-Synuclein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D009930:Organic Chemicals; D051844:alpha-Synuclein