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Histidine is a versatile amino acid with metal-binding, nucleophilic, and basic properties that endow many peptides and proteins with biological activity. However, histidine itself is susceptible to oxidative modifications via post-translational modifications, photooxidation, and metal-catalyzed oxidation. Despite multiple investigations into these different oxidation systems, the varied attributions and differential outcomes point to significant gaps in our understanding of the coordination requirements, spectral features, and reaction products that accompany Cu-catalyzed oxidation of histidine-containing peptides. Here, we use model peptides of Histatin-5, a salivary peptide with Cu-potentiated antifungal activity that relies on its histidine residues, to characterize the complex mixture resulting from reaction with Cu under physiologically relevant reducing and oxidizing conditions. Characterization via LC-MS, MS/MS, and NMR revealed adjacent histidine residues of the bis-His site were the main target of Cu-catalyzed oxidation, with predominant modifications being 2-oxo-His and His-His crosslinks. Doubly- and triply-oxygenated peptides, intramolecular His-His crosslinks, and multimers in the case of a shorter model peptide were also observed. The configuration of the bis-His motif may enable Cu reactivity not available in the other systems where His residues are not adjacent in sequence. These results expand the possibilities of oxidative modifications available to other proteins and peptides containing adjacent histidines. The NMR and MS data here characterized the various histidine modifications. The NMR data describes the protons, carbons, and the correlations between them, which provided rich structural detail for the peptide samples. The MS1 data showed the masses of ions from the native peptide and oxidized peptide products. These MS1 ions were sequenced by tandem MS to yield masses that correlated mass modifications to specific residues of the peptide.... [Read More]
Total Size
3 files (18.5 MB)
Data Citation
Franz, K. J., Bontreger, L. J., Gallo, A. D., Moon, J., Silinski, P., & Monson, E. (2025). Data from: Intramolecular histidine crosslinks formed via copper-catalyzed oxidation of histatin peptides. Duke Research Data Repository. https://doi.org/10.7924/r4nv9q11m.
