NiII‐ATCUN‐Catalyzed Tyrosine Nitration in the Presence of Nitrite and Sulfite

• Published in: Chemistry : a European journal Vol. 25; no. 17; pp. 4309 - 4314
• Main Authors: Maiti, Biplab K., Maia, Luisa B., Moura, Isabel, Moura, José J. G.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 21-03-2019
• Subjects: ATCUN motif; Binding; Chemistry; Copper; Fusion protein; Kinetics; Metabolism; Nickel; Nitration; Nitrogen dioxide; orange protein; Proteins; radicals; Reaction kinetics; Reactive nitrogen species; Sulfite; Sulfur; sulfur metabolism; Tyrosine; tyrosine nitration
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201806228

The nitration of tyrosine residues in proteins represents a specific footprint of the formation of reactive nitrogen species (RNS) in vivo. Here, the fusion product of orange protein (ATCUN‐ORP) was used as an in vitro model system containing an amino terminal Cu(II)‐ and Ni(II)‐binding motif (ATCUN) tag at the N‐terminus and a native tyrosine residue in the metal‐cofactor‐binding region for the formation of 3‐NO2‐Tyr (3‐NT). It is shown that NiII‐ATCUN unusually performs nitration of tyrosine at physiological pH in the presence of the NO2−/SO32−/O2 system, which is revealed by a characteristic absorbance band at 430 nm in basic medium and 350 nm in acidic medium (fingerprint of 3‐NT). Kinetics studies showed that the formation of 3‐NT depends on sulfite concentration over nitrite concentration suggesting key intermediate products, identified as oxysulfur radicals, which are detected by spin‐trap EPR study by using 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO). This study describes a new route in the formation of 3‐NT, which is proposed to be linked with the sulfur metabolism pathway associated with the progression of disease occurrence in vivo.
NiII‐ATCUN in action! The NiII ions bound to the amino terminal Cu(II)‐ and Ni(II)‐binding (ATCUN) motifs in orange protein unusually perform nitration of tyrosine at physiological pH in the presence of the NO2−/SO32−/O2 system over the H2O2/NO2− system. This result may provide the sulfur metabolism pathway to yield 3‐nitrotyrosine, which may be associated with sulfur‐related human diseases in vivo.