title: A unique hetero-hexadecameric architecture displayed by the Escherichia coli O157 PaaA2-ParE2 antitoxin-toxin complex.
abstract: Many bacterial pathogens modulate their metabolic activity, virulence and pathogenicity through so-called "toxin-antitoxin" (TA) modules. The genome of the human pathogen Escherichia coli O157 contains two three-component TA modules related to the known parDE module. Here, we show that the toxin EcParE2 maps in a branch of the RelE/ParE toxin superfamily that is distinct from the branches that contain verified gyrase and ribosome inhibitors. The structure of EcParE2 closely resembles that of Caulobacter crescentus ParE but shows a distinct pattern of conserved surface residues, in agreement with its apparent inability to interact with GyrA. The antitoxin EcPaaA2 is characterized by two α-helices (H1 and H2) that serve as molecular recognition elements to wrap itself around EcParE2. Both EcPaaA2 H1 and H2 are required to sustain a high-affinity interaction with EcParE2 and for the inhibition of EcParE2-mediated killing in vivo. Furthermore, evidence demonstrates that EcPaaA2 H2, but not H1, determines specificity for EcParE2. The initially formed EcPaaA2-EcParE2 heterodimer then assembles into a hetero-hexadecamer, which is stable in solution and is formed in a highly cooperative manner. Together these findings provide novel data on quaternary structure, TA interactions and activity of a hitherto poorly characterized family of TA modules.
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, B-1050 Brussel, Belgium.
authors.forename: Yann G-J
authors.initials: YG
authors.lastname: Sterckx
authors.affiliation: Génétique et Physiologie Bactérienne, Faculté des Sciences, Université Libre de Bruxelles (ULB), 12 rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jové
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, B-1050 Brussel, Belgium.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Shkumatov
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, B-1050 Brussel, Belgium; Génétique et Physiologie Bactérienne, Faculté des Sciences, Université Libre de Bruxelles (ULB), 12 rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium.
authors.forename: Abel
authors.initials: A
authors.lastname: Garcia-Pino
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium.
authors.forename: Lieselotte
authors.initials: L
authors.lastname: Geerts
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, B-1050 Brussel, Belgium.
authors.forename: Maia
authors.initials: M
authors.lastname: De Kerpel
authors.affiliation: Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia.
authors.forename: Jurij
authors.initials: J
authors.lastname: Lah
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, B-1050 Brussel, Belgium.
authors.forename: Henri
authors.initials: H
authors.lastname: De Greve
authors.affiliation: Génétique et Physiologie Bactérienne, Faculté des Sciences, Université Libre de Bruxelles (ULB), 12 rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium.
authors.forename: Laurence
authors.initials: L
authors.lastname: Van Melderen
authors.affiliation: Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium; Structural Biology Research Centre, VIB, Pleinlaan 2, B-1050 Brussel, Belgium. Electronic address: remy.loris@vib-vub.be.
authors.forename: Remy
authors.initials: R
authors.lastname: Loris
mesh_terms: D000595:Amino Acid Sequence; D000992:Antitoxins / Q000737:chemistry*; D001427:Bacterial Toxins / Q000737:chemistry*; D002151:Calorimetry; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray; D027081:DNA Gyrase / Q000737:chemistry; D004768:Enterotoxins / Q000737:chemistry; D019453:Escherichia coli O157 / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010802:Phylogeny; D055503:Protein Multimerization; D020349:Surface Plasmon Resonance
chemical_list: D000992:Antitoxins; D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C000610595:PaaA2 protein, E coli; C000610596:ParE2 protein, E coli; D027081:DNA Gyrase
keywords: RelE/ParE toxin superfamily; molecular recognition; protein structure; protein–protein interaction