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Comparative study of tyrosine radicals in hemoglobin and myoglobins treated with hydrogen peroxide.

ABSTRACT: The reactions of hydrogen peroxide with human methemoglobin, sperm whale metmyoglobin, and horse heart metmyoglobin were studied by electron paramagnetic resonance (EPR) spectroscopy at 10 K and room temperature. The singlet EPR signal, one of the three signals seen in these systems at 10 K, is characterized by a poorly resolved, but still detectable, hyperfine structure that can be used to assign it to a tyrosyl radical. The singlet is detectable as a quintet at room temperature in methemoglobin with identical spectral features to those of the well characterized tyrosyl radical in photosystem II. Hyperfine splitting constants found for Tyr radicals were used to find the rotation angle of the phenoxyl group. Analysis of these angles in the crystal structures suggests that the radical resides on Tyr151 in sperm whale myoglobin, Tyr133 in soybean leghemoglobin, and either alphaTyr42, betaTyr35, or betaTyr130 in hemoglobin. In the sperm whale metmyoglobin Tyr103Phe mutant, there is no detectable tyrosyl radical present. Yet the rotation angle of Tyr103 (134 degrees) is too large to account for the observed EPR spectrum in the wild type. Tyr103 is the closest to the heme. We suggest that Tyr103 is the initial site of the radical, which then rapidly migrates to Tyr151.

SUBMITTER: Svistunenko DA

PROVIDER: S-EPMC1302368 | biostudies-other | 2002 Nov

REPOSITORIES: biostudies-other

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Comparative study of tyrosine radicals in hemoglobin and myoglobins treated with hydrogen peroxide.

Svistunenko Dimitri A DA Dunne Jacqueline J Fryer Michael M Nicholls Peter P Reeder Brandon J BJ Wilson Michael T MT Bigotti Maria Giulia MG Cutruzzolà Francesca F Cooper Chris E CE

Biophysical journal 20021101 5

The reactions of hydrogen peroxide with human methemoglobin, sperm whale metmyoglobin, and horse heart metmyoglobin were studied by electron paramagnetic resonance (EPR) spectroscopy at 10 K and room temperature. The singlet EPR signal, one of the three signals seen in these systems at 10 K, is characterized by a poorly resolved, but still detectable, hyperfine structure that can be used to assign it to a tyrosyl radical. The singlet is detectable as a quintet at room temperature in methemoglobi ...[more]

PMID: 12414716

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Project description:In muscle, reactive oxygen species (ROS) generation increases with strenuous activity, chronic unloading, and inflammatory stimuli; skeletal muscle function is very sensitive to ROS; and there are redox-sensitive signaling pathways. Using myogenic cell cultures, we asked whether hydrogen peroxide (H2O2) induces adaptive changes in skeletal muscle gene expression. H2O2 downregulated or failed to induce antioxidant or apoptotic genes in the myotubes. Instead, H2O2 changed the expression of genes for cytosolic and mitochondrial enzymes, and upregulated inflammatory mediators. Finally, H2O2 had a mostly inhibitory effect on the expression of many transcription factors. The results indicate that mild oxidative stress may induce an adaptive response in skeletal muscle without antioxidant upregulation or apoptosis. Experiment Overall Design: Cell Culture: Experiment Overall Design: C2C12 myoblasts (ATCC, Rockville, MD) were cultured in DMEM supplemented with 10% fetal calf serum at 37°C in 5% CO2. Myoblast differentiation was initiated by switching to differentiation medium (DMEM supplemented with 2% heat-inactivated horse serum) and allowed to continue for 96 hrs. Differentiated myotubes were treated for 2 hours with H2O2 (Sigma-Aldrich, St. Louis, MO) 0, 1, 10, 100, or 1000 uM in DMEM supplemented with 0.5% heat-inactivated horse serum. Experiment Overall Design: cDNA microarrays: Experiment Overall Design: Total RNA was obtained from treated C2C12 myotubes with TRIzol reagent (Invitrogen, Carlsbad, CA) following the manufacturer's recommended protocol.Oligonucleotide microarray studies with Affymetrix Mouse Genome 430A gene chips (n=20 chips) were conducted as described earlier. Microarrays were washed and stained with a streptavidin-bound marker and scanned. Data were analyzed with Affymetrix Microarray Suite 5.0 software. Only genes with consistent absent/present calls in all four independent replicates per group were considered for further analysis. Treatment comparisons were crossed so that each H2O2 sample was compared to each control. The software uses the one-sided Wilcoxon's signed rank test to estimate increase/no change/ decrease difference calls for each pair-wise comparison. Only difference calls consistent in all pair-wise comparisons and with average changes > 1.75 were considered significant, resulting in a conservative list of genes with changed expression levels. Functional classification of genes was based on an extensive literature review.

Dataset Information

Comparative study of tyrosine radicals in hemoglobin and myoglobins treated with hydrogen peroxide.

Publications

Comparative study of tyrosine radicals in hemoglobin and myoglobins treated with hydrogen peroxide.

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