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Title: Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products

Abstract

Hydrogen sulfide is a cardioprotective signaling molecule but is toxic at elevated concentrations. Red blood cells can synthesize H2S but, lacking organelles, cannot dispose of H2S via the mitochondrial sulfide oxidation pathway. We have recently shown that at high sulfide concentrations, ferric hemoglobin oxidizes H2S to a mixture of thiosulfate and iron-bound polysulfides in which the latter species predominates. Here, we report the crystal structure of human hemoglobin containing low spin ferric sulfide, the first intermediate in heme-catalyzed sulfide oxidation. The structure provides molecular insights into why sulfide is susceptible to oxidation in human hemoglobin but is stabilized against it in HbI, a specialized sulfide-carrying hemoglobin from a mollusk adapted to life in a sulfide-rich environment. We have also captured a second sulfide bound at a postulated ligand entry/exit site in the α-subunit of hemoglobin, which, to the best of our knowledge, represents the first direct evidence for this site being used to access the heme iron. Hydrodisulfide, a postulated intermediate at the junction between thiosulfate and polysulfide formation, coordinates ferric hemoglobin and, in the presence of air, generated thiosulfate. At low sulfide/heme iron ratios, the product distribution between thiosulfate and iron-bound polysulfides was approximately equal. The iron-bound polysulfides weremore » unstable at physiological glutathione concentrations and were reduced with concomitant formation of glutathione persulfide, glutathione disulfide, and H2S. Hence, although polysulfides are unlikely to be stable in the reducing intracellular milieu, glutathione persulfide could serve as a persulfide donor for protein persulfidation, a posttranslational modification by which H2S is postulated to signal.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Institutes of Health (NIH)
OSTI Identifier:
1351356
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Biological Chemistry; Journal Volume: 292; Journal Issue: 13
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES

Citation Formats

Vitvitsky, Victor, Yadav, Pramod K., An, Sojin, Seravalli, Javier, Cho, Uhn-Soo, and Banerjee, Ruma. Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products. United States: N. p., 2017. Web. doi:10.1074/jbc.M117.774943.
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Vitvitsky, Victor, Yadav, Pramod K., An, Sojin, Seravalli, Javier, Cho, Uhn-Soo, & Banerjee, Ruma. Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products. United States. doi:10.1074/jbc.M117.774943.
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Vitvitsky, Victor, Yadav, Pramod K., An, Sojin, Seravalli, Javier, Cho, Uhn-Soo, and Banerjee, Ruma. Fri . "Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products". United States. doi:10.1074/jbc.M117.774943.
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@article{osti_1351356,
title = {Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products},
author = {Vitvitsky, Victor and Yadav, Pramod K. and An, Sojin and Seravalli, Javier and Cho, Uhn-Soo and Banerjee, Ruma},
abstractNote = {Hydrogen sulfide is a cardioprotective signaling molecule but is toxic at elevated concentrations. Red blood cells can synthesize H2S but, lacking organelles, cannot dispose of H2S via the mitochondrial sulfide oxidation pathway. We have recently shown that at high sulfide concentrations, ferric hemoglobin oxidizes H2S to a mixture of thiosulfate and iron-bound polysulfides in which the latter species predominates. Here, we report the crystal structure of human hemoglobin containing low spin ferric sulfide, the first intermediate in heme-catalyzed sulfide oxidation. The structure provides molecular insights into why sulfide is susceptible to oxidation in human hemoglobin but is stabilized against it in HbI, a specialized sulfide-carrying hemoglobin from a mollusk adapted to life in a sulfide-rich environment. We have also captured a second sulfide bound at a postulated ligand entry/exit site in the α-subunit of hemoglobin, which, to the best of our knowledge, represents the first direct evidence for this site being used to access the heme iron. Hydrodisulfide, a postulated intermediate at the junction between thiosulfate and polysulfide formation, coordinates ferric hemoglobin and, in the presence of air, generated thiosulfate. At low sulfide/heme iron ratios, the product distribution between thiosulfate and iron-bound polysulfides was approximately equal. The iron-bound polysulfides were unstable at physiological glutathione concentrations and were reduced with concomitant formation of glutathione persulfide, glutathione disulfide, and H2S. Hence, although polysulfides are unlikely to be stable in the reducing intracellular milieu, glutathione persulfide could serve as a persulfide donor for protein persulfidation, a posttranslational modification by which H2S is postulated to signal.},
doi = {10.1074/jbc.M117.774943},
journal = {Journal of Biological Chemistry},
number = 13,
volume = 292,
place = {United States},
year = {Fri Feb 17 00:00:00 EST 2017},
month = {Fri Feb 17 00:00:00 EST 2017}
}
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Journal Article:
DOI:  10.1074/jbc.M117.774943
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    Electron spin resonance (ESR) experiments on the oxidation of hydrogen sulfide were performed in the temperature range 20-150/sup 0/C. Alumina, active carbon, and molecular sieve zeolite 13X were investigated as catalysts. For zeolite 13X it was demonstrated that the reaction is autocatalytic and that sulfur radicals are the active sites for oxygen chemisorption. The intensity of the sulfur radical ESR signal, which is related to the degree of conversion of these radicals, by oxygen, fits in with an oxidation-reduction mechanism. The sulfur-oxygen radical species, which appear when oxygen is admitted to sulfur radicals, are assigned to sulfur chains containing onemore » or two oxygen atoms at the end of the chain. It is very likely that these sulfur-oxygen radicals are intermediates in the proposed mechanism. The formation of the by-product SO/sub 2/ from S/sub x/O/sub 2/.-at temperatures above 175/sup 0/C is also visible in the ESR spectrum. On the basis of the experiments it is concluded that in the mechanism of H/sub 2/S oxidation on active carbons, carbon radicals do not play an important role.« less

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