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Title: A heterodimeric glutathione S -transferase that stereospecifically breaks lignin's β( R )-aryl ether bond reveals the diversity of bacterial β-etherases

Lignin is a heterogeneous polymer of aromatic subunits that is a major component of lignocellulosic plant biomass. Understanding how microorganisms deconstruct lignin is important for understanding the global carbon cycle, and could aid in developing systems for processing plant biomass into valuable commodities. Sphingomonad bacteria use stereospecific glutathione S-transferases (GSTs) called β-etherases to cleave the β-aryl ether (β-O-4) bond, the most common bond between aromatic subunits in lignin. Previously characterized bacterial β-etherases are homodimers that fall into two distinct GST subclasses: LigE homologues, which cleave the β(R) stereoisomer of the bond, and LigF homologues, which cleave the β(S) stereoisomer. Here, we report on a heterodimeric β-etherase (BaeAB) from the sphingomonad Novosphingobium aromaticivorans that stereospecifically cleaves the β(R)-aryl ether bond of the di-aromatic compound β-(2-methoxyphenoxy)-γ-hydroxypropiovanillone (MPHPV). BaeAB’s subunits are phylogenetically distinct from each other and from other β-etherases, though they are evolutionarily related to LigF, despite the fact that BaeAB and LigF cleave different β-aryl ether bond stereoisomers. We identify amino acid residues in BaeAB’s BaeA subunit important for substrate binding and catalysis, including an asparagine that is proposed to activate the glutathione cofactor. We also show that BaeAB homologues from other sphingomonads can cleave β(R)-MPHPV, and that they may bemore » as common in bacteria as LigE homologues. Our results imply that the ability to cleave the β-aryl ether bond arose independently at least twice in GSTs, and that BaeAB homologues may be important for cleaving the β(R)-aryl ether bonds of lignin-derived oligomers in nature.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ; ORCiD logo [2] ;  [1] ;  [3] ; ORCiD logo [4]
  1. Univ. of Wisconsin, Madison, WI (United States). Wisconsin Energy Inst.; Univ. of Wisconsin, Madison, WI (United States). Dept. of Energy Great Lakes Bioenergy Research Center
  2. Univ. of Wisconsin, Madison, WI (United States). Wisconsin Energy Inst.; Univ. of Wisconsin, Madison, WI (United States). Dept. of Energy Great Lakes Bioenergy Research Center; Univ. of Wisconsin, Madison, WI (United States). Dept. of Biochemistry
  3. Univ. of Wisconsin, Madison, WI (United States). Wisconsin Energy Inst.; Univ. of Wisconsin, Madison, WI (United States). Dept. of Energy Great Lakes Bioenergy Research Center; Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering
  4. Univ. of Wisconsin, Madison, WI (United States). Wisconsin Energy Inst.; Univ. of Wisconsin, Madison, WI (United States). Dept. of Energy Great Lakes Bioenergy Research Center; Univ. of Wisconsin, Madison, WI (United States). Dept. of Bacteriology
Publication Date:
Grant/Contract Number:
SC0018409
Type:
Accepted Manuscript
Journal Name:
Journal of Biological Chemistry
Additional Journal Information:
Journal Volume: 294; Journal Issue: 6; Journal ID: ISSN 0021-9258
Publisher:
American Society for Biochemistry and Molecular Biology
Research Org:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
Novosphingobium aromaticivorans; sphingomonads; β-etherase; β-aryl ether bond; glutathione S-transferase; lignin degradation; stereoselectivity; protein evolution; bacterial metabolism; enzyme mutation
OSTI Identifier:
1506668

Kontur, Wayne S., Olmsted, Charles N., Yusko, Larissa M., Niles, Alyssa V., Walters, Kevin A., Beebe, Emily T., Vander Meulen, Kirk A., Karlen, Steven D., Gall, Daniel L., Noguera, Daniel R., and Donohue, Timothy J.. A heterodimeric glutathione S -transferase that stereospecifically breaks lignin's β( R )-aryl ether bond reveals the diversity of bacterial β-etherases. United States: N. p., Web. doi:10.1074/jbc.RA118.006548.
Kontur, Wayne S., Olmsted, Charles N., Yusko, Larissa M., Niles, Alyssa V., Walters, Kevin A., Beebe, Emily T., Vander Meulen, Kirk A., Karlen, Steven D., Gall, Daniel L., Noguera, Daniel R., & Donohue, Timothy J.. A heterodimeric glutathione S -transferase that stereospecifically breaks lignin's β( R )-aryl ether bond reveals the diversity of bacterial β-etherases. United States. doi:10.1074/jbc.RA118.006548.
Kontur, Wayne S., Olmsted, Charles N., Yusko, Larissa M., Niles, Alyssa V., Walters, Kevin A., Beebe, Emily T., Vander Meulen, Kirk A., Karlen, Steven D., Gall, Daniel L., Noguera, Daniel R., and Donohue, Timothy J.. 2018. "A heterodimeric glutathione S -transferase that stereospecifically breaks lignin's β( R )-aryl ether bond reveals the diversity of bacterial β-etherases". United States. doi:10.1074/jbc.RA118.006548. https://www.osti.gov/servlets/purl/1506668.
@article{osti_1506668,
title = {A heterodimeric glutathione S -transferase that stereospecifically breaks lignin's β( R )-aryl ether bond reveals the diversity of bacterial β-etherases},
author = {Kontur, Wayne S. and Olmsted, Charles N. and Yusko, Larissa M. and Niles, Alyssa V. and Walters, Kevin A. and Beebe, Emily T. and Vander Meulen, Kirk A. and Karlen, Steven D. and Gall, Daniel L. and Noguera, Daniel R. and Donohue, Timothy J.},
abstractNote = {Lignin is a heterogeneous polymer of aromatic subunits that is a major component of lignocellulosic plant biomass. Understanding how microorganisms deconstruct lignin is important for understanding the global carbon cycle, and could aid in developing systems for processing plant biomass into valuable commodities. Sphingomonad bacteria use stereospecific glutathione S-transferases (GSTs) called β-etherases to cleave the β-aryl ether (β-O-4) bond, the most common bond between aromatic subunits in lignin. Previously characterized bacterial β-etherases are homodimers that fall into two distinct GST subclasses: LigE homologues, which cleave the β(R) stereoisomer of the bond, and LigF homologues, which cleave the β(S) stereoisomer. Here, we report on a heterodimeric β-etherase (BaeAB) from the sphingomonad Novosphingobium aromaticivorans that stereospecifically cleaves the β(R)-aryl ether bond of the di-aromatic compound β-(2-methoxyphenoxy)-γ-hydroxypropiovanillone (MPHPV). BaeAB’s subunits are phylogenetically distinct from each other and from other β-etherases, though they are evolutionarily related to LigF, despite the fact that BaeAB and LigF cleave different β-aryl ether bond stereoisomers. We identify amino acid residues in BaeAB’s BaeA subunit important for substrate binding and catalysis, including an asparagine that is proposed to activate the glutathione cofactor. We also show that BaeAB homologues from other sphingomonads can cleave β(R)-MPHPV, and that they may be as common in bacteria as LigE homologues. Our results imply that the ability to cleave the β-aryl ether bond arose independently at least twice in GSTs, and that BaeAB homologues may be important for cleaving the β(R)-aryl ether bonds of lignin-derived oligomers in nature.},
doi = {10.1074/jbc.RA118.006548},
journal = {Journal of Biological Chemistry},
number = 6,
volume = 294,
place = {United States},
year = {2018},
month = {12}
}

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