Identification of oxidative modifications of hemopexin and their predicted physiological relevance
| Autor: | Rachel Hunt, Andrew Skaff, Edward S. Bjes, Ann Smith, J. Andrew Keightley, Peter Hahl |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Models
Molecular 0301 basic medicine Heme binding Hypochlorous acid Protein Conformation Heme Oxidative phosphorylation Ligands Biochemistry 03 medical and health sciences chemistry.chemical_compound 0302 clinical medicine Species Specificity Hemopexin Tandem Mass Spectrometry Animals Humans Amino Acid Sequence Tyrosine Molecular Biology Chromatography High Pressure Liquid Conserved Sequence chemistry.chemical_classification Binding Sites Molecular Structure biology Tryptophan Molecular Bases of Disease Cell Biology Rats Amino acid body regions Kinetics 030104 developmental biology chemistry Myeloperoxidase biology.protein Rabbits Apoproteins Reactive Oxygen Species Oxidation-Reduction 030217 neurology & neurosurgery |
| Zdroj: | Journal of Biological Chemistry. 292:13658-13671 |
| ISSN: | 0021-9258 |
| Popis: | Hemopexin protects against heme toxicity in hemolytic diseases and conditions, sepsis, and sickle cell disease. This protection is sustained by heme-hemopexin complexes in biological fluids that resist oxidative damage during heme-driven inflammation. However, apo-hemopexin is vulnerable to inactivation by reactive nitrogen (RNS) and oxygen species (ROS) that covalently modify amino acids. The resultant nitration of amino acids is considered a specific effect reflecting biological events. Using LC-MS, we discovered low endogenous levels of tyrosine nitration in the peptide YYCFQGNQFLR in the heme-binding site of human hemopexin, which was similarly nitrated in rabbit and rat hemopexins. Immunoblotting and selective reaction monitoring were used to quantify tyrosine nitration of in vivo samples and when hemopexin was incubated in vitro with nitrating nitrite/myeloperoxidase/glucose oxidase. Significantly, heme binding by hemopexin declined as tyrosine nitration proceeded in vitro. Three nitrated tyrosines reside in the heme-binding site of hemopexin, and we found that one, Tyr-199, interacts directly with the heme ring D propionate. Investigating the oxidative modifications of amino acids after incubation with tert-butyl hydroperoxide and hypochlorous acid in vitro, we identified additional covalent oxidative modifications on four tyrosine residues and one tryptophan residue of hemopexin. Importantly, three of the four modified tyrosines, some of which have more than one modification, cluster in the heme-binding site, supporting a hierarchy of vulnerable amino acids. We propose that during inflammation, apo-hemopexin is nitrated and oxidated in niches of the body containing activated RNS- and ROS-generating immune and endothelial cells, potentially impairing hemopexin's protective extracellular antioxidant function. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|