Unfolding and aggregation of oxidized metal-deficient superoxide dismutase and isoflavone inhibition based on ion mobility mass spectrometry and ThT fluorescence assay

Abstract

Structurally abnormal Cu, Zn-superoxide dismutase (SOD1) is considered one of the causes of amyotrophic lateral sclerosis. The misfolding and neurotoxic aggregation of SOD1 can be induced by mutations, metal deficiency, and post-translational modification. Here, we revealed the risk of oxidation damage on zinc-deficient SOD1 by native mass spectrometry coupled with ion mobility. The copper ions were found to be released in the early period of oxidation which may be the result of oxidation on its binding site. On the other hand, zinc-deficient SOD1 showed a faster and deeper dissociation tendency than SOD1 with no metal ions. The results of collision-induced unfolding indicated that the oxidized zinc-deficient SOD1 is more easily to be turned into totally unfolded conformation. ThT fluorescence also showed stronger aggregation of oxidized zinc-deficient SOD1. Compared with DTT-induced reduction, oxidized zinc-deficient SOD1 acted differently in dimer dissociation, conformation stability, and aggregation, suggesting that the conserved intramolecular disulfide bonds were influenced little during oxidation. Additionally, we explored glycitin, an isoflavone glycoside, to prevent the oxidation of metal-deficient SOD1 and inhibit the unfolding and aggregation of oxidized metal-deficient SOD1.