The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase

ABSTRACT The protein YfeX from Escherichia coli has been proposed to be essential for the process of iron removal from heme by carrying out a dechelation of heme without cleavage of the porphyrin macrocycle. Since this proposed reaction is unique and would represent the first instance of the biologi...

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Autores principales:	Harry A. Dailey, Alecia N. Septer, Lauren Daugherty, Daniel Thames, Svetlana Gerdes, Eric V. Stabb, Anne K. Dunn, Tamara A. Dailey, John D. Phillips
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2011
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/bdd4bfce0feb408790388fff78b67dbd
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spelling	oai:doaj.org-article:bdd4bfce0feb408790388fff78b67dbd2021-11-15T15:38:48ZThe <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase10.1128/mBio.00248-112150-7511https://doaj.org/article/bdd4bfce0feb408790388fff78b67dbd2011-12-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00248-11https://doaj.org/toc/2150-7511ABSTRACT The protein YfeX from Escherichia coli has been proposed to be essential for the process of iron removal from heme by carrying out a dechelation of heme without cleavage of the porphyrin macrocycle. Since this proposed reaction is unique and would represent the first instance of the biological dechelation of heme, we undertook to characterize YfeX. Our data reveal that YfeX effectively decolorizes the dyes alizarin red and Cibacron blue F3GA and has peroxidase activity with pyrogallal but not guiacol. YfeX oxidizes protoporphyrinogen to protoporphyrin in vitro. However, we were unable to detect any dechelation of heme to free porphyrin with purified YfeX or in cellular extracts of E. coli overexpressing YfeX. Additionally, Vibrio fischeri, an organism that can utilize heme as an iron source when grown under iron limitation, is able to grow with heme as the sole source of iron when its YfeX homolog is absent. Plasmid-driven expression of YfeX in V. fischeri grown with heme did not result in accumulation of protoporphyrin. We propose that YfeX is a typical dye-decolorizing peroxidase (or DyP) and not a dechelatase. The protoporphyrin reported to accumulate when YfeX is overexpressed in E. coli likely arises from the intracellular oxidation of endogenously synthesized protoporphyrinogen and not from dechelation of exogenously supplied heme. Bioinformatic analysis of bacterial YfeX homologs does not identify any connection with iron acquisition but does suggest links to anaerobic-growth-related respiratory pathways. Additionally, some genes encoding homologs of YfeX have tight association with genes encoding a bacterial cytoplasmic encapsulating protein. IMPORTANCE Acquisition of iron from the host during infection is a limiting factor for growth and survival of pathogens. Host heme is the major source of iron in infections, and pathogenic bacteria have evolved complex mechanisms to acquire heme and abstract the iron from heme. Recently Létoffé et al. (Proc. Natl. Acad. Sci. U. S. A. 106:11719–11724, 2009) reported that the protein YfeX from E. coli is able to dechelate heme to remove iron and leave an intact tetrapyrrole. This is totally unlike any other described biological system for iron removal from heme and, thus, would represent a dramatically new feature with potentially profound implications for our understanding of bacterial pathogenesis. Given that this reaction has no precedent in biological systems, we characterized YfeX and a related protein. Our data clearly demonstrate that YfeX is not a dechelatase as reported but is a peroxidase that oxidizes endogenous porphyrinogens to porphyrins.Harry A. DaileyAlecia N. SepterLauren DaughertyDaniel ThamesSvetlana GerdesEric V. StabbAnne K. DunnTamara A. DaileyJohn D. PhillipsAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 2, Iss 6 (2011)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Harry A. Dailey Alecia N. Septer Lauren Daugherty Daniel Thames Svetlana Gerdes Eric V. Stabb Anne K. Dunn Tamara A. Dailey John D. Phillips The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase
description	ABSTRACT The protein YfeX from Escherichia coli has been proposed to be essential for the process of iron removal from heme by carrying out a dechelation of heme without cleavage of the porphyrin macrocycle. Since this proposed reaction is unique and would represent the first instance of the biological dechelation of heme, we undertook to characterize YfeX. Our data reveal that YfeX effectively decolorizes the dyes alizarin red and Cibacron blue F3GA and has peroxidase activity with pyrogallal but not guiacol. YfeX oxidizes protoporphyrinogen to protoporphyrin in vitro. However, we were unable to detect any dechelation of heme to free porphyrin with purified YfeX or in cellular extracts of E. coli overexpressing YfeX. Additionally, Vibrio fischeri, an organism that can utilize heme as an iron source when grown under iron limitation, is able to grow with heme as the sole source of iron when its YfeX homolog is absent. Plasmid-driven expression of YfeX in V. fischeri grown with heme did not result in accumulation of protoporphyrin. We propose that YfeX is a typical dye-decolorizing peroxidase (or DyP) and not a dechelatase. The protoporphyrin reported to accumulate when YfeX is overexpressed in E. coli likely arises from the intracellular oxidation of endogenously synthesized protoporphyrinogen and not from dechelation of exogenously supplied heme. Bioinformatic analysis of bacterial YfeX homologs does not identify any connection with iron acquisition but does suggest links to anaerobic-growth-related respiratory pathways. Additionally, some genes encoding homologs of YfeX have tight association with genes encoding a bacterial cytoplasmic encapsulating protein. IMPORTANCE Acquisition of iron from the host during infection is a limiting factor for growth and survival of pathogens. Host heme is the major source of iron in infections, and pathogenic bacteria have evolved complex mechanisms to acquire heme and abstract the iron from heme. Recently Létoffé et al. (Proc. Natl. Acad. Sci. U. S. A. 106:11719–11724, 2009) reported that the protein YfeX from E. coli is able to dechelate heme to remove iron and leave an intact tetrapyrrole. This is totally unlike any other described biological system for iron removal from heme and, thus, would represent a dramatically new feature with potentially profound implications for our understanding of bacterial pathogenesis. Given that this reaction has no precedent in biological systems, we characterized YfeX and a related protein. Our data clearly demonstrate that YfeX is not a dechelatase as reported but is a peroxidase that oxidizes endogenous porphyrinogens to porphyrins.
format	article
author	Harry A. Dailey Alecia N. Septer Lauren Daugherty Daniel Thames Svetlana Gerdes Eric V. Stabb Anne K. Dunn Tamara A. Dailey John D. Phillips
author_facet	Harry A. Dailey Alecia N. Septer Lauren Daugherty Daniel Thames Svetlana Gerdes Eric V. Stabb Anne K. Dunn Tamara A. Dailey John D. Phillips
author_sort	Harry A. Dailey
title	The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase
title_short	The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase
title_full	The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase
title_fullStr	The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase
title_full_unstemmed	The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase
title_sort	<named-content content-type="genus-species">escherichia coli</named-content> protein yfex functions as a porphyrinogen oxidase, not a heme dechelatase
publisher	American Society for Microbiology
publishDate	2011
url	https://doaj.org/article/bdd4bfce0feb408790388fff78b67dbd
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The <named-content content-type="genus-species">Escherichia coli</named-content> Protein YfeX Functions as a Porphyrinogen Oxidase, Not a Heme Dechelatase

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