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Tyrosine residues as redox cofactors in human hemoglobin : implications for engineering nontoxic blood substitutes

Reeder, Brandon J; Grey, Marie LU ; Silaghi-Dumitrescu, Radu-Lucian; Svistunenko, Dimitri A; Bülow, Leif LU ; Cooper, Chris E and Wilson, Michael T (2008) In Journal of Biological Chemistry 283(45). p.30780-30787
Abstract

Respiratory proteins such as myoglobin and hemoglobin can, under oxidative conditions, form ferryl heme iron and protein-based free radicals. Ferryl myoglobin can safely be returned to the ferric oxidation state by electron donation from exogenous reductants via a mechanism that involves two distinct pathways. In addition to direct transfer between the electron donor and ferryl heme edge, there is a second pathway that involves "through-protein" electron transfer via a tyrosine residue (tyrosine 103, sperm whale myoglobin). Here we show that the heterogeneous subunits of human hemoglobin, the alpha and beta chains, display significantly different kinetics for ferryl reduction by exogenous reductants. By using selected hemoglobin... (More)

Respiratory proteins such as myoglobin and hemoglobin can, under oxidative conditions, form ferryl heme iron and protein-based free radicals. Ferryl myoglobin can safely be returned to the ferric oxidation state by electron donation from exogenous reductants via a mechanism that involves two distinct pathways. In addition to direct transfer between the electron donor and ferryl heme edge, there is a second pathway that involves "through-protein" electron transfer via a tyrosine residue (tyrosine 103, sperm whale myoglobin). Here we show that the heterogeneous subunits of human hemoglobin, the alpha and beta chains, display significantly different kinetics for ferryl reduction by exogenous reductants. By using selected hemoglobin mutants, we show that the alpha chain possesses two electron transfer pathways, similar to myoglobin. Furthermore, tyrosine 42 is shown to be a critical component of the high affinity, through-protein electron transfer pathway. We also show that the beta chain of hemoglobin, lacking the homologous tyrosine, does not possess this through-protein electron transfer pathway. However, such a pathway can be engineered into the protein by mutation of a specific phenylalanine residue to a tyrosine. High affinity through-protein electron transfer pathways, whether native or engineered, enhance the kinetics of ferryl removal by reductants, particularly at low reductant concentrations. Ferryl iron has been suggested to be a major cause of the oxidative toxicity of hemoglobin-based blood substitutes. Engineering hemoglobin with enhanced rates of ferryl removal, as we show here, is therefore likely to result in molecules better suited for in vivo oxygen delivery.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Animals, Blood Substitutes, Electron Transport, Free Radicals, Hemoglobins, Horses, Humans, Iron, Kinetics, Myoglobin, Oxidation-Reduction, Oxygen, Protein Engineering, Protein Subunits, Sperm Whale, Tyrosine
in
Journal of Biological Chemistry
volume
283
issue
45
pages
8 pages
publisher
ASBMB
external identifiers
  • scopus:56949088820
ISSN
0021-9258
DOI
10.1074/jbc.M804709200
language
English
LU publication?
yes
id
7b3b7e70-1661-4580-bcba-e7a04ff59e79
date added to LUP
2016-04-18 15:52:14
date last changed
2017-08-06 05:06:13
@article{7b3b7e70-1661-4580-bcba-e7a04ff59e79,
  abstract     = {<p>Respiratory proteins such as myoglobin and hemoglobin can, under oxidative conditions, form ferryl heme iron and protein-based free radicals. Ferryl myoglobin can safely be returned to the ferric oxidation state by electron donation from exogenous reductants via a mechanism that involves two distinct pathways. In addition to direct transfer between the electron donor and ferryl heme edge, there is a second pathway that involves "through-protein" electron transfer via a tyrosine residue (tyrosine 103, sperm whale myoglobin). Here we show that the heterogeneous subunits of human hemoglobin, the alpha and beta chains, display significantly different kinetics for ferryl reduction by exogenous reductants. By using selected hemoglobin mutants, we show that the alpha chain possesses two electron transfer pathways, similar to myoglobin. Furthermore, tyrosine 42 is shown to be a critical component of the high affinity, through-protein electron transfer pathway. We also show that the beta chain of hemoglobin, lacking the homologous tyrosine, does not possess this through-protein electron transfer pathway. However, such a pathway can be engineered into the protein by mutation of a specific phenylalanine residue to a tyrosine. High affinity through-protein electron transfer pathways, whether native or engineered, enhance the kinetics of ferryl removal by reductants, particularly at low reductant concentrations. Ferryl iron has been suggested to be a major cause of the oxidative toxicity of hemoglobin-based blood substitutes. Engineering hemoglobin with enhanced rates of ferryl removal, as we show here, is therefore likely to result in molecules better suited for in vivo oxygen delivery.</p>},
  author       = {Reeder, Brandon J and Grey, Marie and Silaghi-Dumitrescu, Radu-Lucian and Svistunenko, Dimitri A and Bülow, Leif and Cooper, Chris E and Wilson, Michael T},
  issn         = {0021-9258},
  keyword      = {Animals,Blood Substitutes,Electron Transport,Free Radicals,Hemoglobins,Horses,Humans,Iron,Kinetics,Myoglobin,Oxidation-Reduction,Oxygen,Protein Engineering,Protein Subunits,Sperm Whale,Tyrosine},
  language     = {eng},
  month        = {11},
  number       = {45},
  pages        = {30780--30787},
  publisher    = {ASBMB},
  series       = {Journal of Biological Chemistry},
  title        = {Tyrosine residues as redox cofactors in human hemoglobin : implications for engineering nontoxic blood substitutes},
  url          = {http://dx.doi.org/10.1074/jbc.M804709200},
  volume       = {283},
  year         = {2008},
}