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Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin

FIC domain proteins mediate post-translational modifications of target proteins, which typically results in their inactivation. Depending on the conservation of crucial active site residues, the FIC fold serves as structural scaffold for various enzymatic activities, mostly target adenylylation. The...

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Autores principales: Stanger, Frédéric V., Harms, Alexander, Dehio, Christoph, Schirmer, Tilman
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5033356/
https://www.ncbi.nlm.nih.gov/pubmed/27657533
http://dx.doi.org/10.1371/journal.pone.0163654
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author Stanger, Frédéric V.
Harms, Alexander
Dehio, Christoph
Schirmer, Tilman
author_facet Stanger, Frédéric V.
Harms, Alexander
Dehio, Christoph
Schirmer, Tilman
author_sort Stanger, Frédéric V.
collection PubMed
description FIC domain proteins mediate post-translational modifications of target proteins, which typically results in their inactivation. Depending on the conservation of crucial active site residues, the FIC fold serves as structural scaffold for various enzymatic activities, mostly target adenylylation. The founding member of the vast Fic protein family, EcFicT, was identified in Escherichia coli some time ago. The G55R point mutant of EcFicT displays the “filamentation induced by cAMP” (Fic) phenotype at high 3',5'-cyclic adenosine monophosphate (cAMP) concentrations and elevated temperature, but the underlying molecular mechanism and any putative biochemical activity of EcFicT have remained unknown. EcFicT belongs to class I Fic toxin proteins that are encoded together with a small inhibitory protein (antitoxin), named EcFicA in E. coli. Here, we report the crystal structures of two mutant EcFicT/EcFicA complexes (EcFicT(G55R)A and EcFicTA(E28G)) both showing close resemblance with the structure of the AMP-transferase VbhT from Bartonella schoenbuchensis in complex with its cognate antitoxin VbhA. However, crucial differences in the active site of EcFicT compared to VbhT and other AMP-transferases rationalize the lack of evidence for adenylylation activity. Comprehensive bioinformatic analysis suggests that EcFicT has evolved from canonical AMP-transferases and has acquired a conserved binding site for a yet to be discovered novel substrate. The G55R mutation has no effect on structure or thermal stability of EcFicT, such that the molecular basis for its associated Fic phenotype remains elusive. We anticipate that this structure will inspire further bioinformatic and experimental analyses in order to characterize the enzymatic activity of EcFicT and help revealing its physiological role.
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spelling pubmed-50333562016-10-10 Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin Stanger, Frédéric V. Harms, Alexander Dehio, Christoph Schirmer, Tilman PLoS One Research Article FIC domain proteins mediate post-translational modifications of target proteins, which typically results in their inactivation. Depending on the conservation of crucial active site residues, the FIC fold serves as structural scaffold for various enzymatic activities, mostly target adenylylation. The founding member of the vast Fic protein family, EcFicT, was identified in Escherichia coli some time ago. The G55R point mutant of EcFicT displays the “filamentation induced by cAMP” (Fic) phenotype at high 3',5'-cyclic adenosine monophosphate (cAMP) concentrations and elevated temperature, but the underlying molecular mechanism and any putative biochemical activity of EcFicT have remained unknown. EcFicT belongs to class I Fic toxin proteins that are encoded together with a small inhibitory protein (antitoxin), named EcFicA in E. coli. Here, we report the crystal structures of two mutant EcFicT/EcFicA complexes (EcFicT(G55R)A and EcFicTA(E28G)) both showing close resemblance with the structure of the AMP-transferase VbhT from Bartonella schoenbuchensis in complex with its cognate antitoxin VbhA. However, crucial differences in the active site of EcFicT compared to VbhT and other AMP-transferases rationalize the lack of evidence for adenylylation activity. Comprehensive bioinformatic analysis suggests that EcFicT has evolved from canonical AMP-transferases and has acquired a conserved binding site for a yet to be discovered novel substrate. The G55R mutation has no effect on structure or thermal stability of EcFicT, such that the molecular basis for its associated Fic phenotype remains elusive. We anticipate that this structure will inspire further bioinformatic and experimental analyses in order to characterize the enzymatic activity of EcFicT and help revealing its physiological role. Public Library of Science 2016-09-22 /pmc/articles/PMC5033356/ /pubmed/27657533 http://dx.doi.org/10.1371/journal.pone.0163654 Text en © 2016 Stanger et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Stanger, Frédéric V.
Harms, Alexander
Dehio, Christoph
Schirmer, Tilman
Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin
title Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin
title_full Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin
title_fullStr Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin
title_full_unstemmed Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin
title_short Crystal Structure of the Escherichia coli Fic Toxin-Like Protein in Complex with Its Cognate Antitoxin
title_sort crystal structure of the escherichia coli fic toxin-like protein in complex with its cognate antitoxin
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5033356/
https://www.ncbi.nlm.nih.gov/pubmed/27657533
http://dx.doi.org/10.1371/journal.pone.0163654
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