The mode of interaction of ataxin-3 Q36 (AT-3 Q36) with selected endogenous and exogenous metal ions, namely, $Zn^{2+}$, $Cu^{2+}$, $Ni^{2+}$, and $Cd^{2+}$, was examined. Metal-ion-induced structural changes of the protein were monitored by fluorescence as well as Fourier transform Raman spectroscopy. We found that the cations tested lead to a decrease in $\alpha$-helical content and a concurrent increase in $\beta$-sheet as well as undefined ($\beta$-turn and random-coil) structures. The most evident effect was observed for copper and nickel cations. After titration with these cations, the AT3 Q36 secondary structure content (27% $\alpha$-helices in the presence of either ion, 31 and 27% $\beta$-sheets for $Cu^{2+}$ and $Ni^{2+}$, respectively) was similar to that observed for the aggregated form of the protein (27% $\alpha$-helices, 36% $\beta$-sheets). Using the 1-anilinonaphthalene-8-sulfonate hydrophobic fluorescence probe, we showed that the presence of the metal ions tested led to the formation of solvent-exposed hydrophobic patches of AT-3 Q36, and that such an effect decreased with increasing ionic radius.
keywords in English:
ataxin-3, Fourier transform Raman, metal ions, secondary structures
affiliation:
Wydział Chemii : Zakład Chemii Nieorganicznej, Wydział Chemii : Zakład Fizyki Chemicznej