ORCID Profile
0000-0002-7733-6982
Current Organisation
Instegrated Structural Biology Grenoble - ISBG
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Publisher: Springer Science and Business Media LLC
Date: 04-04-2019
DOI: 10.1038/S41467-019-09355-Y
Abstract: Phox homology (PX) domains are membrane interacting domains that bind to phosphatidylinositol phospholipids or phosphoinositides, markers of organelle identity in the endocytic system. Although many PX domains bind the canonical endosome-enriched lipid PtdIns3 P , others interact with alternative phosphoinositides, and a precise understanding of how these specificities arise has remained elusive. Here we systematically screen all human PX domains for their phospholipid preferences using liposome binding assays, biolayer interferometry and isothermal titration calorimetry. These analyses define four distinct classes of human PX domains that either bind specifically to PtdIns3 P , non-specifically to various di- and tri-phosphorylated phosphoinositides, bind both PtdIns3 P and other phosphoinositides, or associate with none of the lipids tested. A comprehensive evaluation of PX domain structures reveals two distinct binding sites that explain these specificities, providing a basis for defining and predicting the functional membrane interactions of the entire PX domain protein family.
Publisher: Proceedings of the National Academy of Sciences
Date: 13-06-2011
Abstract: Erythroid Krüppel-like factor (EKLF) plays an important role in erythroid development by stimulating β-globin gene expression. We have examined the details by which the minimal transactivation domain (TAD) of EKLF (EKLFTAD) interacts with several transcriptional regulatory factors. We report that EKLFTAD displays homology to the p53TAD and, like the p53TAD, can be ided into two functional subdomains (EKLFTAD1 and EKLFTAD2). Based on sequence analysis, we found that EKLFTAD2 is conserved in KLF2, KLF4, KLF5, and KLF15. In addition, we demonstrate that EKLFTAD2 binds the amino-terminal PH domain of the Tfb1 62 subunit of TFIIH (Tfb1PH 62PH) and four domains of CREB-binding protein 300. The solution structure of the EKLFTAD2/Tfb1PH complex indicates that EKLFTAD2 binds Tfb1PH in an extended conformation, which is in contrast to the α-helical conformation seen for p53TAD2 in complex with Tfb1PH. These studies provide detailed mechanistic information into EKLFTAD functions as well as insights into potential interactions of the TADs of other KLF proteins. In addition, they suggest that not only have acidic TADs evolved so that they bind using different conformations on a common target, but that transitioning from a disordered to a more ordered state is not a requirement for their ability to bind multiple partners.
Publisher: MDPI AG
Date: 25-09-2020
DOI: 10.3390/V12101075
Abstract: The study of viruses causing acute respiratory distress syndromes (ARDS) is more essential than ever at a time when a virus can create a global pandemic in a matter of weeks. Among human adenoviruses, adenovirus of serotype 7 (HAdV7) is one of the most virulent serotypes. This virus regularly re-emerges in Asia and has just been the cause of several deaths in the United States. A critical step of the virus life cycle is the attachment of the knob domain of the fiber (HAd7K) to the cellular receptor desmoglein-2 (DSG2). Complexes between the fiber knob and two extracellular domains of DSG2 have been produced. Their characterization by biochemical and biophysical methods show that these two domains are sufficient for the interaction and that the trimeric HAd7K could accommodate up to three DSG2 receptor molecules. The cryo-electron microscopy (cryo-EM) structure of these complexes at 3.1 Å resolution confirmed the biochemical data, and allowed the identification of the critical amino acid residues for this interaction, which shows similarities with other DSG2 interacting adenoviruses, despite a low homology in the primary sequences.
Publisher: American Chemical Society (ACS)
Date: 17-07-2008
DOI: 10.1021/JA800975H
Publisher: Elsevier BV
Date: 05-2020
Publisher: Cold Spring Harbor Laboratory
Date: 03-11-2021
DOI: 10.1101/2021.11.03.467097
Abstract: The apicomplexa comprise a large phylum of single-celled, obligate intracellular protozoa that infect humans and animals and cause severe parasitic diseases. Available therapeutics against these devastating diseases are limited by suboptimal efficacy and frequent side effects, as well as the emergence and spread of resistance. Here, we use a drug repurposing strategy and identify altiratinib, a compound originally developed to treat glioblastoma, as a promising drug candidate with broad spectrum activity against apicomplexans. Altiratinib is parasiticidal and blocks the development of intracellular zoites in the nanomolar range and with a high selectivity index. We have identified Tg PRP4K of T. gondii as the primary target of altiratinib by genetic target deconvolution, highlighting key residues within the kinase catalytic site that, when mutated, confer resistance to the drug. We have further elucidated the molecular basis of the inhibitory mechanism and species selectivity of altiratinib for Tg PRP4K as well as for its P. falciparum counterpart Pf CLK3. Our data also point to structural features critical for binding of the other Pf CLK3 inhibitor, TCMDC-135051. Consistent with the role of this kinase family in splicing in a broad spectrum of eukaryotes, we have shown that altiratinib causes global disruption of splicing, primarily through intron retention in both T. gondii and P. falciparum . Thus, our data establish parasitic PRP4K/CLK3 as a promising pan-apicomplexan target whose repertoire of inhibitors can be expanded by the addition of altiratinib.
Publisher: eLife Sciences Publications, Ltd
Date: 15-07-2021
DOI: 10.7554/ELIFE.68312
Abstract: Correct 3’end processing of mRNAs is one of the regulatory cornerstones of gene expression. In a parasite that must adapt to the regulatory requirements of its multi-host life style, there is a need to adopt additional means to partition the distinct transcriptional signatures of the closely and tandemly arranged stage-specific genes. In this study, we report our findings in T. gondii of an m6A-dependent 3’end polyadenylation serving as a transcriptional barrier at these loci . We identify the core polyadenylation complex within T. gondii and establish CPSF4 as a reader for m6A-modified mRNAs, via a YTH domain within its C-terminus, a feature which is shared with plants. We bring evidence of the specificity of this interaction both biochemically, and by determining the crystal structure at high resolution of the T. gondii CPSF4-YTH in complex with an m6A-modified RNA. We show that the loss of m6A, both at the level of its deposition or its recognition is associated with an increase in aberrantly elongated chimeric mRNAs emanating from impaired transcriptional termination, a phenotype previously noticed in the plant model Arabidopsis thaliana . Nanopore direct RNA sequencing shows the occurrence of transcriptional read-through breaching into downstream repressed stage-specific genes, in the absence of either CPSF4 or the m6A RNA methylase components in both T. gondii and A. thaliana . Taken together, our results shed light on an essential regulatory mechanism coupling the pathways of m6A metabolism directly to the cleavage and polyadenylation processes, one that interestingly seem to serve, in both T. gondii and A. thaliana , as a guardian against aberrant transcriptional read-throughs.
Publisher: Springer Science and Business Media LLC
Date: 24-01-2019
DOI: 10.1038/S41598-018-37306-Y
Abstract: This paper focuses on the nucleoprotein (NP) of the newly identified member of the Orthomyxoviridae family, Influenza D virus. To date several X-ray structures of NP of Influenza A (A/NP) and B (B/NP) viruses and of infectious salmon anemia (ISA/NP) virus have been solved. Here we purified, characterized and solved the X-ray structure of the tetrameric D/NP at 2.4 Å resolution. The crystal structure of its core is similar to NP of other Influenza viruses. However, unlike A/NP and B/NP which possess a flexible amino-terminal tail containing nuclear localization signals (NLS) for their nuclear import, D/NP possesses a carboxy-terminal tail (D/NP TAIL ). We show that D/NP TAIL harbors a bipartite NLS and designed C-terminal truncated mutants to demonstrate the role of D/NP TAIL for nuclear transport.
Publisher: Proceedings of the National Academy of Sciences
Date: 08-01-2008
Abstract: The general transcription factor IIH is recruited to the transcription preinitiation complex through an interaction between its p62/Tfb1 subunit and the α-subunit of the general transcription factor IIE (TFIIEα). We have determined that the acidic carboxyl terminus of TFIIEα (TFIIEα 336–439 ) directly binds the amino-terminal PH domain of p62/Tfb1 with nanomolar affinity. NMR mapping and mutagenesis studies demonstrate that the TFIIEα binding site on p62/Tfb1 is identical to the binding site for the second transactivation domain of p53 (p53 TAD2). In addition, we demonstrate that TFIIEα 336–439 is capable of competing with p53 for a common binding site on p62/Tfb1 and that TFIIEα 336–439 and the diphosphorylated form (pS46 T55) of p53 TAD2 have similar binding constants. NMR structural studies reveal that TFIIEα 336–439 contains a small domain (residues 395–433) folded in a novel ββααα topology. NMR mapping studies demonstrate that two unstructured regions (residues 377–393 and residues 433–439) located on either side of the folded domain appear to be required for TFIIEα 336–439 binding to p62/Tfb1 and that these two unstructured regions are held close to each other in three-dimensional space by the novel structured domain. We also demonstrate that, like p53, TFIIEα 336–439 can activate transcription in vivo . These results point to an important interplay between the general transcription factor TFIIEα and the tumor suppressor protein p53 in regulating transcriptional activation that may be modulated by the phosphorylation status of p53.
Publisher: Springer Science and Business Media LLC
Date: 13-01-2021
DOI: 10.1038/S41598-020-79611-5
Abstract: Francisella tularensis is one of the most virulent pathogenic bacteria causing the acute human respiratory disease tularemia. While the mechanisms underlying F. tularensis pathogenesis are largely unknown, previous studies have shown that a F. novicida transposon mutant with insertions in a gene coding for a putative lysine decarboxylase was attenuated in mouse spleen, suggesting a possible role of its protein product as a virulence factor. Therefore, we set out to structurally and functionally characterize the F. novicida lysine decarboxylase , which we termed LdcF . Here, we investigate the genetic environment of ldcF as well as its evolutionary relationships with other basic AAT-fold amino acid decarboxylase superfamily members, known as key actors in bacterial adaptative stress response and polyamine biosynthesis. We determine the crystal structure of LdcF and compare it with the most thoroughly studied lysine decarboxylase, E. coli LdcI . We analyze the influence of ldcF deletion on bacterial growth under different stress conditions in dedicated growth media, as well as in infected macrophages, and demonstrate its involvement in oxidative stress resistance. Finally, our mass spectrometry-based quantitative proteomic analysis enables identification of 80 proteins with expression levels significantly affected by ldcF deletion, including several DNA repair proteins potentially involved in the diminished capacity of the F. novicida mutant to deal with oxidative stress. Taken together, we uncover an important role of LdcF in F. novicida survival in host cells through participation in oxidative stress response, thereby singling out this previously uncharacterized protein as a potential drug target.
Publisher: Springer Science and Business Media LLC
Date: 21-04-2021
DOI: 10.1007/S00249-021-01532-6
Abstract: Microscale thermophoresis (MST), and the closely related Temperature Related Intensity Change (TRIC), are synonyms for a recently developed measurement technique in the field of biophysics to quantify biomolecular interactions, using the (capillary-based) NanoTemper Monolith and (multiwell plate-based) Dianthus instruments. Although this technique has been extensively used within the scientific community due to its low s le consumption, ease of use, and ubiquitous applicability, MST/TRIC has not enjoyed the unambiguous acceptance from biophysicists afforded to other biophysical techniques like isothermal titration calorimetry (ITC) or surface plasmon resonance (SPR). This might be attributed to several facts, e.g., that various (not fully understood) effects are contributing to the signal, that the technique is licensed to only a single instrument developer, NanoTemper Technology, and that its reliability and reproducibility have never been tested independently and systematically. Thus, a working group of ARBRE-MOBIEU has set up a benchmark study on MST/TRIC to assess this technique as a method to characterize biomolecular interactions. Here we present the results of this study involving 32 scientific groups within Europe and two groups from the US, carrying out experiments on 40 Monolith instruments , employing a standard operation procedure and centrally prepared s les. A protein–small molecule interaction, a newly developed protein–protein interaction system and a pure dye were used as test systems. We characterized the instrument properties and evaluated instrument performance, reproducibility, the effect of different analysis tools, the influence of the experimenter during data analysis, and thus the overall reliability of this method.
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.PEP.2014.09.019
Abstract: TRAM/TICAM-2 is used by Toll-like receptor 4 (TLR4) as a bridging adaptor during the mammalian innate immune response. It recruits TRIF, another TIR domain-containing adaptor protein, to TLR4 via TIR domain interactions, which leads to the activation of transcription factors responsible for the production of type-1 interferon and cytokines. The molecular mechanisms of these dual interactions mediated by the TRAM TIR domain are not clear. To understand the molecular basis of TIR:TIR domain interactions, structural and biochemical studies of TRAM TIR domain are necessary, and require a functional soluble protein. In this paper, we report a successful purification and characterization of full-length TRAM. Because full-length TRAM likely contains unstructured regions that may be disadvantageous for structural studies, we also carried out a systematic construct design to determine the boundaries of the TRAM TIR domain. The truncated TRAM constructs were designed based on secondary structure predictions and screened by small-scale expression. Selected constructs were subjected to biophysical analyses. We show that the expressed TRAM TIR domain is functional using in vitro GST pull-down assays that demonstrate a physical interaction with the TLR4 TIR domain. We further show, by site-directed mutagenesis, that the "BB loop" regions of both the TRAM TIR domain and the TLR4 TIR domain are crucial for this physical interaction.
Publisher: MDPI AG
Date: 16-12-2022
DOI: 10.3390/V14122813
Abstract: As for all non-segmented negative RNA viruses, rabies virus has its genome packaged in a linear assembly of nucleoprotein (N), named nucleocapsid. The formation of new nucleocapsids during virus replication in cells requires the production of soluble N protein in complex with its phosphoprotein (P) chaperone. In this study, we reconstituted a soluble heterodimeric complex between an armless N protein of rabies virus (RABV), lacking its N-terminal subdomain (NNT-ARM), and a peptide encompassing the N0 chaperon module of the P protein. We showed that the chaperone module undergoes a disordered−order transition when it assembles with N0 and measured an affinity in the low nanomolar range using a competition assay. We solved the crystal structure of the complex at a resolution of 2.3 Å, unveiling the details of the conserved interfaces. MD simulations showed that both the chaperon module of P and RNA-mediated polymerization reduced the ability of the RNA binding cavity to open and close. Finally, by reconstituting a complex with full-length P protein, we demonstrated that each P dimer could independently chaperon two N0 molecules.
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.JSB.2019.07.006
Abstract: The NAD(P)-dependent malate dehydrogenases (MalDHs) and NAD-dependent lactate dehydrogenases (LDHs) are homologous enzymes involved in central metabolism. They display a common protein fold and the same catalytic mechanism, yet have a stringent capacity to discriminate between their respective substrates. The MalDH/LDH superfamily is ided into several phylogenetically related groups. It has been shown that the canonical LDHs and LDH-like group of MalDHs are primarily tetrameric enzymes that erged from a common ancestor. In order to gain understanding of the evolutionary history of the LDHs and MalDHs, the biochemical properties and crystallographic structure of the LDH-like MalDH from the hyperthermophilic archaeon Ignicoccus islandicus (I. isl) were determined. I. isl MalDH recognizes oxaloacetate as main substrate, but it is also able to use pyruvate. Surprisingly, with pyruvate, the enzymatic activity profile looks like that of allosteric LDHs, suggesting a hidden allosteric capacity in a MalDH. The I. isl MalDH tetrameric structure in the apo state is considerably different from those of canonical LDH-like MalDHs and LDHs, representing an alternative oligomeric organization. A comparison with MalDH and LDH counterparts provides strong evidence that the ergence between allosteric and non-allosteric members of the superfamily involves homologs with intermediate, atypical properties.
Publisher: Elsevier BV
Date: 03-2021
DOI: 10.1016/J.JSB.2020.107689
Abstract: S100A9, with its congener S100A8, belongs to the S100 family of calcium-binding proteins found exclusively in vertebrates. These two proteins are major constituents of neutrophils. In response to a pathological condition, they can be released extracellularly and become alarmins that induce both pro- and anti-inflammatory signals, through specific cell surface receptors. They also act as antimicrobial agents, mainly as a S100A8/A9 heterocomplex, through metal sequestration. The mechanisms whereby alent cations modulate the extracellular functions of S100A8 and S100A9 are still unclear. Importantly, it has been proposed that these ions may affect both the ternary and quaternary structure of these proteins, thereby influencing their physiological properties. In the present study, we report the crystal structures of WT and C80A murine S100A9 (mS100A9), determined at 1.45 and 2.35 Å resolution, respectively, in the presence of calcium and zinc. These structures reveal a canonical homodimeric form for the protein. They also unravel an intramolecular disulfide bridge that stabilizes the C-terminal tail in a rigid conformation, thus shaping a second Zn-binding site per S100A9 protomer. In solution, mS100A9 apparently binds only two zinc ions per homodimer, with an affinity in the micromolar range, and aggregates in the presence of excess zinc. Using mass spectrometry, we demonstrate that mS100A9 can form both non-covalent and covalent homodimers with distinct disulfide bond patterns. Interestingly, calcium and zinc seem to affect differentially the relative proportion of these forms. We discuss how the metal-dependent interconversion between mS100A9 homodimers may explain the versatility of physiological functions attributed to the protein.
Publisher: Springer Science and Business Media LLC
Date: 10-09-2018
DOI: 10.1038/S41598-018-31634-9
Abstract: The plant hormone auxin regulates numerous aspects of the plant life cycle. Auxin signalling is mediated by auxin response factors (ARFs) that dimerise with modulating Aux/IAA repressors. ARF3 (ETTIN or ETT) is atypical as it does not interact with Aux/IAA repressors. It is proposed to be a non-canonical auxin sensor, regulating erse functions essential for development. This sensing ability relies on a unique C-terminal ETT specific domain (ES domain). Alignments of ETT orthologues across the angiosperm phylum revealed that the length and sequence identities of ES domains are poorly conserved. Computational predictors suggested the ES domains to be intrinsically disordered, explaining their tolerance of insertions, deletions and mutations during evolution. Nevertheless, five highly conserved short linear motifs were identified suggesting functional significance. High-throughput library screening identified an almost full-length soluble ES domain that did not bind auxin directly, but exhibited a dose-dependent response in a yeast two-hybrid system against the Arabidopsis INDEHISCENT (IND) transcription factor. Circular dichroism confirmed the domain was disordered. The identification and purification of this domain opens the way to the future characterisation of the ETT auxin-sensing mechanism in planta and an improved understanding of auxin-mediated regulation.
Publisher: Oxford University Press (OUP)
Date: 09-2022
Abstract: We unveil the intimate relationship between protein dynamics and allostery by following the trajectories of model proteins in their conformational and sequence spaces. Starting from a nonallosteric hyperthermophilic malate dehydrogenase, we have tracked the role of protein dynamics in the evolution of the allosteric capacity. Based on a large phylogenetic analysis of the malate (MalDH) and lactate dehydrogenase (LDH) superfamily, we identified two amino acid positions that could have had a major role for the emergence of allostery in LDHs, which we targeted for investigation by site-directed mutagenesis. Wild-type MalDH and the single and double mutants were tested with respect to their substrate recognition profiles. The double mutant displayed a sigmoid-shaped profile typical of homotropic activation in LDH. By using molecular dynamics simulations, we showed that the mutations induce a drastic change in the protein s ling of its conformational landscape, making transiently T-like (inactive) conformers, typical of allosteric LDHs, accessible. Our data fit well with the seminal key concept linking protein dynamics and evolvability. We showed that the selection of a new phenotype can be achieved by a few key dynamics-enhancing mutations causing the enrichment of low-populated conformational substates.
Publisher: Springer Science and Business Media LLC
Date: 08-05-2012
DOI: 10.1007/S12104-011-9313-6
Abstract: VERNALIZATION1 (VRN1) is a multidomain DNA binding protein from Arabidopsis thaliana that is required for the acceleration of flowering time in response to prolonged cold treatment a physiological process called vernalization. VRN1 is a 39 kDa protein comprised of two B3 domains flanking a putative nuclear localization sequence and two PEST domains. Here we report the (1)H, (13)C and (15)N resonance assignments of the 134 residue C-terminal region of VRN1, comprising a B3 DNA binding domain of the REM family and an upstream region that is highly conserved among VRN1 homologs from other dicotyledonous plant species.
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.JMB.2022.167551
Abstract: To understand the dynamic interactions between the phosphoprotein (P) and the nucleoprotein (N) within the transcription/replication complex of the Paramyxoviridae and to decipher their roles in regulating viral multiplication, we characterized the structural properties of the C-terminal X domain (P
Publisher: Proceedings of the National Academy of Sciences
Date: 18-08-2014
Abstract: Cell surface proteins are regulated by a constant cycle of internalization and recycling from intracellular compartments called endosomes. From these organelles, two protein sorting platforms, sorting nexin 27 (SNX27) and the retromer complex, play a critical role in the retrieval of various proteins responsible for ion transport, glucose metabolism, neurotransmission, and other cell functions. Based on the three-dimensional structure of SNX27 in complex with the retromer subunit VPS26, we define the mechanism by which these proteins cooperate to drive endosomal cargo sorting. Retromer and SNX27 dysfunction is implicated in various disorders, including diabetes, Down syndrome, Parkinson disease, and Alzheimer’s disease, and this work provides important insights into the assembly of this essential endosomal sorting machinery.
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.JSB.2018.09.010
Abstract: The Gram-positive bacterium Bacillus subtilis responds to starvation by entering a morphological differentiation process leading to the formation of a highly resistant spore. Early in the sporulation process, the cell asymmetrically ides into a large compartment (the mother cell) and a smaller one (the forespore), which will maturate into a resistant spore. Proper development of the forespore requires the assembly of a multiprotein complex called the SpoIIIA-SpoIIQ complex or "A-Q complex". This complex involves the forespore protein SpoIIQ and eight mother cell proteins (SpoIIIAA to SpoIIIAH), many of which share structural similarities with components of specialized secretion systems and flagella found in Gram-negative bacteria. The assembly of the A-Q complex across the two membranes that separate the mother cell and forespore was recently shown to require GerM. GerM is a lipoprotein composed of two GerMN domains, a family of domains with unknown function. Here, we report X-ray crystallographic structures of the first GerMN domain of GerM at 1.0 Å resolution, and of the soluble domain of GerM (the tandem of GerMN domains) at 2.1 Å resolution. These structures reveal that GerMN domains can adopt distinct conformations and that the core of these domains display structural similarities with ring-building motifs found in components of specialized secretion system and in SpoIIIA proteins. This work provides an additional piece towards the structural characterization of the A-Q complex.
Publisher: American Society of Hematology
Date: 02-07-2009
DOI: 10.1182/BLOOD-2008-10-180489
Abstract: In addition to orchestrating the expression of all erythroid-specific genes, GATA-1 controls the growth, differentiation, and survival of the erythroid lineage through the regulation of genes that manipulate the cell cycle and apoptosis. The stages of mammalian erythropoiesis include global gene inactivation, nuclear condensation, and enucleation to yield circulating erythrocytes, and some of the genes whose expression are altered by GATA-1 during this process are members of the p53 pathway. In this study, we demonstrate a specific in vitro interaction between the transactivation domain of p53 (p53TAD) and a segment of the GATA-1 DNA-binding domain that includes the carboxyl-terminal zinc-finger domain. We also show by immunoprecipitation that the native GATA-1 and p53 interact in erythroid cells and that activation of p53-responsive promoters in an erythroid cell line can be inhibited by the overexpression of GATA-1. Mutational analysis reveals that GATA-1 inhibition of p53 minimally requires the segment of the GATA-1 DNA-binding domain that interacts with p53TAD. This inhibition is reciprocal, as the activation of a GATA-1–responsive promoter can be inhibited by p53. Based on these findings, we conclude that inhibition of the p53 pathway by GATA-1 may be essential for erythroid cell development and survival.
Publisher: Springer Science and Business Media LLC
Date: 22-05-2012
DOI: 10.1007/S12104-012-9390-1
Abstract: Proteins containing a domain of unknown function 59 (DUF59) appear to have a variety of physiological functions, ranging from iron-sulfur cluster assembly to DNA repair. DUF59 proteins have been found in bacteria, archaea and eukaryotes, however Fam96a and Fam96b are the only mammalian proteins predicted to contain a DUF59 domain. Fam96a is an 18 kDa protein comprised primarily of a DUF59 domain (residues 31-157) and an N-terminal signal peptide (residues 1-27). Interestingly, the DUF59 domain of Fam96a exists as monomeric and dimeric forms in solution, and X-ray crystallography studies of both forms unexpectedly revealed two different domain-swapped dimer structures. Here we report the backbone resonance assignments and secondary structure of the monomeric form of the 127 residue DUF59 domain of human Fam96a. This study provides the basis for further understanding the structural variability exhibited by Fam96a and the mechanism for domain swapping.
Publisher: Elsevier BV
Date: 03-2022
DOI: 10.1016/J.JSB.2021.107813
Abstract: Components of specialized secretion systems, which span the inner and outer membranes in Gram-negative bacteria, include ring-forming proteins whose oligomerization was proposed to be promoted by domains called RBM for "Ring-Building Motifs". During spore formation in Gram-positive bacteria, a transport system called the SpoIIIA-SpoIIQ complex also assembles in the double membrane that surrounds the forespore following its endocytosis by the mother cell. The presence of RBM domains in some of the SpoIIIA proteins led to the hypothesis that they would assemble into rings connecting the two membranes and form a conduit between the mother cell and forespore. Among them, SpoIIIAG forms homo-oligomeric rings in vitro but the oligomerization of other RBM-containing SpoIIIA proteins, including SpoIIIAH, remains to be demonstrated. In this work, we identified RBM domains in the YhcN/YlaJ family of proteins that are not related to the SpoIIIA-SpoIIQ complex. We solved the crystal structure of YhcN from Bacillus subtilis, which confirmed the presence of a RBM fold, flanked by additional secondary structures. As the protein did not show any oligomerization ability in vitro, we investigated the structural determinants of ring formation in SpoIIIAG, SpoIIIAH and YhcN. We showed that in vitro, the conserved core of RBM domains alone is not sufficient for oligomerization while the β-barrel forming region in SpoIIIAG forms rings on its own. This work suggests that some RBMs might indeed participate in the assembly of homomeric rings but others might have evolved toward other functions.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-08-2022
DOI: 10.1126/SCITRANSLMED.ABN3231
Abstract: The Apicomplexa comprise a large phylum of single-celled, obligate intracellular protozoa that include
Publisher: Springer Science and Business Media LLC
Date: 05-04-2022
DOI: 10.1038/S42003-022-03276-1
Abstract: Bacterial homologous lysine and arginine decarboxylases play major roles in the acid stress response, physiology, antibiotic resistance and virulence. The Escherichia coli enzymes are considered as their archetypes. Whereas acid stress triggers polymerisation of the E. coli lysine decarboxylase LdcI, such behaviour has not been observed for the arginine decarboxylase Adc. Here we show that the Adc from a multidrug-resistant human pathogen Providencia stuartii massively polymerises into filaments whose cryo-EM structure reveals pronounced differences between Adc and LdcI assembly mechanisms. While the structural determinants of Adc polymerisation are conserved only in certain Providencia and Burkholderia species , acid stress-induced polymerisation of LdcI appears general for enterobacteria. Analysis of the expression, activity and oligomerisation of the P. stuartii Adc further highlights the distinct properties of this unusual protein and lays a platform for future investigation of the role of supramolecular assembly in the superfamily or arginine and lysine decarboxylases.
Publisher: Springer Science and Business Media LLC
Date: 28-04-2023
Publisher: Springer Science and Business Media LLC
Date: 04-07-2018
DOI: 10.1038/S41467-018-05053-3
Abstract: The liver-specific microRNA-122 (miR-122) recognizes two conserved sites at the 5′ end of the hepatitis C virus (HCV) genome and contributes to stability, translation, and replication of the viral RNA. We show that stimulation of the HCV internal ribosome entry site (IRES) by miR-122 is essential for efficient viral replication. The mechanism relies on a dual function of the 5′ terminal sequence in the complementary positive (translation) and negative strand (replication), requiring different secondary structures. Predictions and experimental evidence argue for several alternative folds involving the miR-binding region (MBR) adjacent to the IRES and interfering with its function. Mutations in the MBR, designed to suppress these dysfunctional structures indeed stimulate translation independently of miR-122. Conversely, MBR mutants favoring alternative folds show impaired IRES activity. Our results therefore suggest that miR-122 binding assists the folding of a functional IRES in an RNA chaperone-like manner by suppressing energetically favorable alternative secondary structures.
Publisher: Springer Science and Business Media LLC
Date: 05-09-2016
DOI: 10.1038/NSMB.3290
Abstract: Recycling of internalized receptors from endosomal compartments is essential for the receptors' cell-surface homeostasis. Sorting nexin 27 (SNX27) cooperates with the retromer complex in the recycling of proteins containing type I PSD95-Dlg-ZO1 (PDZ)-binding motifs. Here we define specific acidic amino acid sequences upstream of the PDZ-binding motif required for high-affinity engagement of the human SNX27 PDZ domain. However, a subset of SNX27 ligands, such as the β
Location: Canada
No related grants have been discovered for Caroline Mas.