Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8268015 | Free Radical Biology and Medicine | 2016 | 13 Pages |
Abstract
We investigated the combined effect of ascorbate and copper [Asc/Cu(II)] on the integrity of bovine [Cu-Zn]-superoxide dismutase (bSOD1) as a model system to study the metal catalyzed oxidation (MCO) and fragmentation of proteins. We found Asc/Cu(II) mediates specific cleavage of bSOD1 and generates 12.5 and 3.2 kDa fragments in addition to oxidation/carbonylation of the protein. The effect of other tested transition metals, a metal chelator, and hydrogen peroxide on the cleavage and oxidation indicated that binding of copper to a previously unknown site on SOD1 is responsible for the Asc/Cu(II) specific cleavage and oxidation. We utilized tandem mass spectrometry to identify the specific cleavage sites of Asc/Cu(II)-treated bSOD1. Analyses of tryptic- and AspN-peptides have demonstrated the cleavage to occur at Gly31 with peptide bond breakage with Thr30 and Ser32 through diamide and α-amidation pathways, respectively. The three-dimensional structure of bSOD1 reveals the imidazole ring of His19 localized within 5 Ã
from the α-carbon of Gly31 providing a structural basis that copper ion, most likely coordinated by His19, catalyzes the specific cleavage reaction.
Keywords
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Authors
Hiroshi Uehara, Shen Luo, Baikuntha Aryal, Rodney L. Levine, V. Ashutosh Rao,