Abel Garcia-Pino

Free University of Brussels, Bruxelles, Brussels Capital Region, Belgium

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Publications (39)283.19 Total impact

  • Remy Loris, Abel Garcia-Pino
    Chemical Reviews 05/2014; · 41.30 Impact Factor
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    ABSTRACT: Antitoxins from prokaryotic type II toxin-antitoxin modules are characterized by a high degree of intrinsic disorder. The description of such highly flexible proteins is challenging because they cannot be represented by a single structure. Here, we present a combination of SAXS and NMR data to describe the conformational ensemble of the PaaA2 antitoxin from the human pathogen E. coli O157. The method encompasses the use of SAXS data to filter ensembles out of a pool of conformers generated by a custom NMR structure calculation protocol and the subsequent refinement by a block jackknife procedure. The final ensemble obtained through the method is validated by an established residual dipolar coupling analysis. We show that the conformational ensemble of PaaA2 is highly compact and that the protein exists in solution as two preformed helices, connected by a flexible linker, that probably act as molecular recognition elements for toxin inhibition.
    Structure 04/2014; · 5.99 Impact Factor
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    ABSTRACT: The Staphylococcus aureus genome contains three toxin-antitoxin modules, including one mazEF module, SamazEF. Using an on-column separation protocol we are able to obtain large amounts of wild-type SaMazF toxin. The protein is well-folded and highly resistant against thermal unfolding but aggregates at elevated temperatures. Crystallographic and nuclear magnetic resonance (NMR) solution studies show a well-defined dimer. Differences in structure and dynamics between the X-ray and NMR structural ensembles are found in three loop regions, two of which undergo motions that are of functional relevance. The same segments also show functionally relevant dynamics in the distantly related CcdB family despite divergence of function. NMR chemical shift mapping and analysis of residue conservation in the MazF family suggests a conserved mode for the inhibition of MazF by MazE.
    Nucleic Acids Research 04/2014; · 8.81 Impact Factor
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    ABSTRACT: Transfer ribonucleic acid (tRNA) modifications, especially at the wobble position, are crucial for proper and efficient protein translation. MnmE and MnmG form a protein complex that is implicated in the carboxymethylaminomethyl modification of wobble uridine (cmnm(5)U34) of certain tRNAs. MnmE is a G protein activated by dimerization (GAD), and active guanosine-5'-triphosphate (GTP) hydrolysis is required for the tRNA modification to occur. Although crystal structures of MnmE and MnmG are available, the structure of the MnmE/MnmG complex (MnmEG) and the nature of the nucleotide-induced conformational changes and their relevance for the tRNA modification reaction remain unknown. In this study, we mainly used small-angle X-ray scattering to characterize these conformational changes in solution and to unravel the mode of interaction between MnmE, MnmG and tRNA. In the nucleotide-free state MnmE and MnmG form an unanticipated asymmetric α2β2 complex. Unexpectedly, GTP binding promotes further oligomerization of the MnmEG complex leading to an α4β2 complex. The transition from the α2β2 to the α4β2 complex is fast, reversible and coupled to GTP binding and hydrolysis. We propose a model in which the nucleotide-induced changes in conformation and oligomerization of MnmEG form an integral part of the tRNA modification reaction cycle.
    Nucleic Acids Research 03/2014; · 8.81 Impact Factor
  • Abel Garcia-Pino, Nikolay Zenkin, Remy Loris
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    ABSTRACT: Fic enzymes post-translationally modify proteins through AMPylation, UMPylation, phosphorylation, or phosphocholination. They have been identified across all domains of life, and they target a myriad of proteins such as eukaryotic GTPases, unstructured protein segments, and bacterial enzymes. Consequently, they play crucial roles in eukaryotic signal transduction, drug tolerance, bacterial pathogenicity, and the bacterial stress response. Structurally, they consist of an all α-helical core domain that supports and scaffolds a structurally conserved active-site loop, which catalyses the transfer of various parts of a nucleotide cofactor to proteins. Despite their diverse substrates and targets, they retain a conserved active site and reaction chemistry. This catalytic variety came to light only recently with the crystal structures of different Fic enzymes.
    Trends in Biochemical Sciences 02/2014; · 13.08 Impact Factor
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    ABSTRACT: Uropathogenic Escherichia coli cause urinary tract infections by adhering to mannosylated receptors on the human urothelium via the carbohydrate-binding domain of the FimH adhesin (FimHL). Numerous α D mannopyranosides, including α-D-heptyl mannose (HM), inhibit this process by interacting with FimHL. To establish the molecular basis of the high-affinity HM binding, we solved the solution structure of the apo form and the crystal structure of the FimHL-HM complex. NMR relaxation analysis revealed that protein dynamics were not affected by the sugar binding, yet HM addition promoted protein dimerization, which was further confirmed by small angle X-ray scattering. Finally, to address the role of Y48 - part of the "tyrosine gate" believed to govern the affinity and specificity of mannoside binding - we characterized the FimHL Y48A mutant, whose conformational, dynamical, and HM binding properties were found to be very similar to those of the wild-type protein.
    Journal of Medicinal Chemistry 01/2014; · 5.61 Impact Factor
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    ABSTRACT: TAX1BP1 is a novel ubiquitin-binding adaptor protein involved in the negative regulation of the NF-kappaB transcription factor, which is a key player in inflammatory responses, immunity and tumorigenesis. TAX1BP1 recruits A20 to the ubiquitinated signalling proteins TRAF6 and RIP1, leading to their A20-mediated deubiquitination and the disruption of IL-1 and TNF-induced NF-kappaB signalling, respectively. The two zinc fingers localized at its C-terminal, function as novel ubiquitin binding domains (UBZ, ubiquitin binding zinc finger). Here we present for the first time both the solution and crystal structures of two classical UBZ domains in tandem within the human TAX1BP1. The relative orientation of the two domains is slightly different in the X-ray structure with respect to the NMR structure, indicating some degree of conformational flexibility, which is rationalized by NMR relaxation data. The observed degree of flexibility and stability between the two UBZ domains might have consequences on the recognition mechanism of interacting partners.
    Journal of Molecular Biology 11/2013; · 3.91 Impact Factor
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    ABSTRACT: Fic proteins are ubiquitous in all of the domains of life and have critical roles in multiple cellular processes through AMPylation of (transfer of AMP to) target proteins. Doc from the doc-phd toxin-antitoxin module is a member of the Fic family and inhibits bacterial translation by an unknown mechanism. Here we show that, in contrast to having AMPylating activity, Doc is a new type of kinase that inhibits bacterial translation by phosphorylating the conserved threonine (Thr382) of the translation elongation factor EF-Tu, rendering EF-Tu unable to bind aminoacylated tRNAs. We provide evidence that EF-Tu phosphorylation diverged from AMPylation by antiparallel binding of the NTP relative to the catalytic residues of the conserved Fic catalytic core of Doc. The results bring insights into the mechanism and role of phosphorylation of EF-Tu in bacterial physiology as well as represent an example of the catalytic plasticity of enzymes and a mechanism for the evolution of new enzymatic activities.
    Nature Chemical Biology 10/2013; · 12.95 Impact Factor
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    ABSTRACT: The genome of Vibrio cholerae encodes two higBA toxin-antitoxin (TA) modules that are activated by amino-acid starvation. Here, the TA complex of the second module, higBA2, as well as the C-terminal domain of the corresponding HigA2 antitoxin, have been purified and crystallized. The HigBA2 complex crystallized in two crystal forms. Crystals of form I belonged to space group P21212, with unit-cell parameters a = 129.0, b = 119.8, c = 33.4 Å, and diffracted to 3.0 Å resolution. The asymmetric unit is likely to contain a single complex consisting of two toxin monomers and one antitoxin dimer. The second crystal form crystallized in space group P3221, with unit-cell parameters a = 134.5, c = 55.4 Å. These crystals diffracted to 2.2 Å resolution and probably contain a complex with a different stoichiometry. Crystals of the C-terminal domain of HigA2 belonged to space group C2, with unit-cell parameters a = 115.4, b = 61.2, c = 73.8 Å, β = 106.7°, and diffracted to 1.8 Å resolution.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 09/2013; 69(Pt 9):1052-9. · 0.55 Impact Factor
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    Acta Crystallographica Section F Structural Biology and Crystallization Communications 07/2013; Accepted. · 0.55 Impact Factor
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    ABSTRACT: The CD2AP and CIN85 adaptor proteins each employ three SH3 domains to cluster protein partners and ensure efficient signal transduction and downregulation of tyrosine kinase receptors. Using NMR, ITC and SAXS methods, we have characterized several binding modes of the N-terminal SH3 domain (SH3A) of CD2AP and CIN85 against two natural atypical proline-rich ligands from CD2 and Cbl-b and compared and contrasted these data with previous studies and published crystal structures. Our experiments show that the CD2AP-SH3A domain forms a type II dimer with CD2 and both a type I and type II dimeric complex with Cbl-b. Like CD2AP, the CIN85-SH3A domain forms a type II complex with CD2, but a trimeric complex with Cbl-b where the interactions type I and II take place at the same time. Together, these results explain how multiple interactions among similar SH3 domains and ligands can produce a high degree of diversity in tyrosine kinase, cell adhesion or T-cell triggering signaling pathways. This article is protected by copyright. All rights reserved.
    FEBS Journal 05/2013; · 4.25 Impact Factor
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    ABSTRACT: Toxin–antitoxin (TA) modules in bacteria are involved in pathogenesis, antibiotic stress response, persister formation and programmed cell death. The toxin Doc, from the phd/doc module, blocks protein synthesis by targeting the translation machinery. Despite a large wealth of biophysical and biochemical data on the regulatory aspects of the operon transcription and role of Doc co-activator and co-repressor, little is still know on the molecular basis of Doc toxicity. Structural information about this toxin is only available for its inhibited state bound to the antitoxin Phd. Here we report the 1H, 15N and 13C backbone and side chain chemical shift assignments of the toxin Doc from of bacteriophage P1 (the model protein from this family of TA modules) in its free state. The BMRB accession number is 18899.
    Biomolecular NMR Assignments 02/2013; · 0.64 Impact Factor
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    ABSTRACT: Lectin-like bacteriotoxic proteins, identified in several plant-associated bacteria, are able to selectively kill closely related species, including several phytopathogens, such as and species, but so far their mode of action remains unrevealed. The crystal structure of LlpA, the prototype lectin-like bacteriocin from , reveals an architecture of two monocot mannose-binding lectin (MMBL) domains and a C-terminal β-hairpin extension. The C-terminal MMBL domain (C-domain) adopts a fold very similar to MMBL domains from plant lectins and contains a binding site for mannose and oligomannosides. Mutational analysis indicates that an intact sugar-binding pocket in this domain is crucial for bactericidal activity. The N-terminal MMBL domain (N-domain) adopts the same fold but is structurally more divergent and lacks a functional mannose-binding site. Differential activity of engineered N/C-domain chimers derived from two LlpA homologues with different killing spectra, disclosed that the N-domain determines target specificity. Apparently this bacteriocin is assembled from two structurally similar domains that evolved separately towards dedicated functions in target recognition and bacteriotoxicity.
    PLoS Pathogens 02/2013; 9(2):e1003199. · 8.14 Impact Factor
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    ABSTRACT: N-Carbamoyl-l-amino acid amidohydrolases (l-carbamoylases) are important industrial enzymes used in kinetic resolution of racemic mixtures of N-carbamoyl-amino acids due to their strict enantiospecificity. In this work, we report the first l-carbamoylase structure belonging to Geobacillus stearothermophilus CECT43 (BsLcar), at a resolution of 2.7 Å. Structural analysis of BsLcar and several members of the peptidase M20/M25/M40 family confirmed the expected conserved residues at the active site in this family, and site-directed mutagenesis revealed their relevance to substrate binding. We also found an unexpectedly conserved arginine residue (Arg(234) in BsLcar), proven to be critical for dimerization of the enzyme. The mutation of this sole residue resulted in a total loss of activity and prevented the formation of the dimer in BsLcar. Comparative studies revealed that the dimerization domain of the peptidase M20/M25/M40 family is a "small-molecule binding domain," allowing further evolutionary considerations for this enzyme family.
    Journal of bacteriology 08/2012; 194(21):5759-68. · 3.94 Impact Factor
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    ABSTRACT: S-layers are regular two-dimensional semipermeable protein layers that constitute a major cell-wall component in archaea and many bacteria. The nanoscale repeat structure of the S-layer lattices and their self-assembly from S-layer proteins (SLPs) have sparked interest in their use as patterning and display scaffolds for a range of nano-biotechnological applications. Despite their biological abundance and the technological interest in them, structural information about SLPs is limited to truncated and assembly-negative proteins. Here we report the X-ray structure of the SbsB SLP of Geobacillus stearothermophilus PV72/p2 by the use of nanobody-aided crystallization. SbsB consists of a seven-domain protein, formed by an amino-terminal cell-wall attachment domain and six consecutive immunoglobulin-like domains, that organize into a φ-shaped disk-like monomeric crystallization unit stabilized by interdomain Ca(2+) ion coordination. A Ca(2+)-dependent switch to the condensed SbsB quaternary structure pre-positions intermolecular contact zones and renders the protein competent for S-layer assembly. On the basis of crystal packing, chemical crosslinking data and cryo-electron microscopy projections, we present a model for the molecular organization of this SLP into a porous protein sheet inside the S-layer. The SbsB lattice represents a previously undescribed structural model for protein assemblies and may advance our understanding of SLP physiology and self-assembly, as well as the rational design of engineered higher-order structures for biotechnology.
    Nature 06/2012; 487(7405):119-22. · 38.60 Impact Factor
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    ABSTRACT: Escherichia coli O157 paaR2-paaA2-parE2 constitutes a unique three-component toxin-antitoxin (TA) module encoding a toxin (ParE2) related to the classic parDE family but with an unrelated antitoxin called PaaA2. The complex between PaaA2 and ParE2 was purified and characterized by analytical gel filtration, dynamic light scattering and small-angle X-ray scattering. It consists of a particle with a radius of gyration of 3.95 nm and is likely to form a heterododecamer. Crystals of the ParE2-PaaA2 complex diffract to 3.8 Å resolution and belong to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 142.9, c = 87.5 Å. The asymmetric unit is consistent with a particle of around 125 kDa, which is compatible with the solution data. Therefore, the ParE2-PaaA2 complex is the largest toxin-antitoxin complex identified to date and its quaternary arrangement is likely to be of biological significance.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 06/2012; 68(Pt 6):724-9. · 0.55 Impact Factor
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    ABSTRACT: Toxin-antitoxin (TA) modules are small operons associated with stress response of bacteria. F-plasmid CcdB(F) was the first TA toxin for which its target, gyrase, was identified. Plasmidic and chromosomal CcdBs belong to distinct families. Conserved residues crucial for gyrase poisoning activity of plasmidic CcdBs are not conserved among these families. Here we show that the chromosomal CcdB(Vfi) from Vibrio fischeri is an active gyrase poison that interacts with its target via an alternative energetic mechanism. Changes in the GyrA14-binding surface of the Vibrio and F-plasmid CcdB family members illustrate neutral drift where alternative interactions can be used to achieve the same functionality. Differences in affinity between V. fischeri and F-plasmid CcdB for gyrase and their corresponding CcdA antitoxin possibly reflect distinct roles for TA modules located on plasmids and chromosomes.
    Molecular Microbiology 05/2012; 84(5):965-78. · 4.96 Impact Factor
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    ABSTRACT: SH2 domains are widespread protein-binding modules that recognize phosphotyrosines and play central roles in intracellular signalling pathways. The SH2 domain of the human protein tyrosine kinase Fyn has been expressed, purified and crystallized in the unbound state and in complex with a high-affinity phosphotyrosine peptide. X-ray data were collected to a resolution of 2.00 Å for the unbound form and 1.40 Å for the protein in complex with the phosphotyrosine peptide.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 03/2012; 68(Pt 3):359-64. · 0.55 Impact Factor
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    ABSTRACT: Proteases carry out a number of crucial functions inside and outside the cell. To protect the cells against the potentially lethal activities of these enzymes, specific inhibitors are produced to tightly regulate the protease activity. Independent reports suggest that the Kunitz-soybean trypsin inhibitor (STI) family has the potential to inhibit proteases with different specificities. In this study, we use a combination of biophysical methods to define the structural basis of the interaction of papaya protease inhibitor (PPI) with serine proteases. We show that PPI is a multiple-headed inhibitor; a single PPI molecule can bind two trypsin units at the same time. Based on sequence and structural analysis, we hypothesize that the inherent plasticity of the β-trefoil fold is paramount in the functional evolution of this family toward multiple protease inhibition.
    Journal of Biological Chemistry 12/2011; 286(51):43726-34. · 4.65 Impact Factor
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    ABSTRACT: Regulation of the phd/doc toxin-antitoxin operon involves the toxin Doc as co- or derepressor depending on the ratio between Phd and Doc, a phenomenon known as conditional cooperativity. The mechanism underlying this observed behavior is not understood. Here we show that monomeric Doc engages two Phd dimers on two unrelated binding sites. The binding of Doc to the intrinsically disordered C-terminal domain of Phd structures its N-terminal DNA-binding domain, illustrating allosteric coupling between highly disordered and highly unstable domains. This allosteric effect also couples Doc neutralization to the conditional regulation of transcription. In this way, higher levels of Doc tighten repression up to a point where the accumulation of toxin triggers the production of Phd to counteract its action. Our experiments provide the basis for understanding the mechanism of conditional cooperative regulation of transcription typical of toxin-antitoxin modules. This model may be applicable for the regulation of other biological systems.
    Cell 07/2010; 142(1):101-11. · 31.96 Impact Factor