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  • Journal article
    Lee W-C, Matthews S, Garnett JA, 2016,

    Crystal structure and analysis of HdaB: the Enteroaggregative Escherichia coli AAF/IV pilus tip protein

    , Protein Science, Vol: 25, Pages: 1898-1905, ISSN: 1469-896X

    Enteroaggregative Escherichia coli is the primary cause of pediatric diarrhea indeveloping countries and utilize aggregative adherence fimbriae (AAFs) to promoteinitial adherence to the host intestinal mucosa, promote the formation of biofilms andmediate host invasion. Five AAFs have been identified to date and AAF/IV is amongstthe most prevalent found in clinical isolates. Here we present the X-ray crystal structureof the AAF/IV tip protein HdaB at 2.0 Å resolution. It shares high structural homologywith members of the Afa/Dr superfamily of fimbriae, which are involved in hostinvasion. We highlight surface exposed residues that share sequence homology andpropose that these may function in invasion and also non-conserved regions that couldmediate HdaB specific adhesive functions.

  • Journal article
    Rasheed M, Garnett J, Perez-Dorado I, Muhl D, Filloux A, Matthews Set al., 2016,

    Crystal structure of the CupB6 adhesive tip from the chaperone-usher family of pili from Pseudomonas aeruginosa

    , Biochimica et Biophysica Acta - Protein Structure, Vol: 1864, Pages: 1500-1505, ISSN: 0005-2795

    Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen that can cause chronicinfection of the lungs of cystic fibrosis patients. Chaperone-usher systems in P. aeruginosa are knownto translocate and assemble adhesive pili on the bacterial surface and contribute to biofilm formationwithin the host. Here, we report the crystal structure of the tip adhesion subunit CupB6 from thecupB1-6 gene cluster. The tip domain is connected to the pilus via the N-terminal donor strand fromthe main pilus subunit CupB1. Although the CupB6 adhesion domain bears structural features similarto other CU adhesins it displays an unusual polyproline helix adjacent to a prominent surface pocket,which are likely the site for receptor recognition.

  • Journal article
    Kierdorf K, Dionne MS, 2016,

    The software and hardware of macrophages: a diversity of options

    , Developmental Cell, Vol: 38, Pages: 122-125, ISSN: 1878-1551

    Macrophages play important immune and homeostatic roles that depend on the ability to receive and interpret specific signals from environmental stimuli. Here we describe the different activation states these cells can exhibit in response to signals and how these states affect and can be affected by bacterial pathogens.

  • Journal article
    Pruneda JN, Durkin CH, Geurink PP, Ovaa H, Santhanam B, Holden DW, Komander Det al., 2016,

    The molecular basis for ubiquitin and ubiquitin-like specificities in bacterial effector proteases

    , Molecular Cell, Vol: 63, Pages: 261-276, ISSN: 1097-2765

    Pathogenic bacteria rely on secreted effector proteins to manipulate host signaling pathways, often in creative ways. CE clan proteases, specific hydrolases for ubiquitin-like modifications (SUMO and NEDD8) in eukaryotes, reportedly serve as bacterial effector proteins with deSUMOylase, deubiquitinase, or, even, acetyltransferase activities. Here, we characterize bacterial CE protease activities, revealing K63-linkage-specific deubiquitinases in human pathogens, such as Salmonella, Escherichia, and Shigella, as well as ubiquitin/ubiquitin-like cross-reactive enzymes in Chlamydia, Rickettsia, and Xanthomonas. Five crystal structures, including ubiquitin/ubiquitin-like complexes, explain substrate specificities and redefine relationships across the CE clan. Importantly, this work identifies novel family members and provides key discoveries among previously reported effectors, such as the unexpected deubiquitinase activity in Xanthomonas XopD, contributed by an unstructured ubiquitin binding region. Furthermore, accessory domains regulate properties such as subcellular localization, as exemplified by a ubiquitin-binding domain in Salmonella Typhimurium SseL. Our work both highlights and explains the functional adaptations observed among diverse CE clan proteins.

  • Journal article
    Yu XJ, Liu M, Holden D, 2016,

    Salmonella Effectors SseF and SseG Interact with Mammalian Protein ACBD3 (GCP60) To Anchor Salmonella-Containing Vacuoles at the Golgi Network

    , mBio, Vol: 7, ISSN: 2161-2129

    Following infection of mammalian cells, Salmonella enterica serovar Typhimurium (S. Typhimurium) replicates within membrane-bound compartments known as Salmonella-containing vacuoles (SCVs). The Salmonella pathogenicity island 2 type III secretion system (SPI-2 T3SS) translocates approximately 30 different effectors across the vacuolar membrane. SseF and SseG are two such effectors that are required for SCVs to localize close to the Golgi network in infected epithelial cells. In a yeast two-hybrid assay, SseG and an N-terminal variant of SseF interacted directly with mammalian ACBD3, a multifunctional cytosolic Golgi network-associated protein. Knockdown of ACBD3 by small interfering RNA (siRNA) reduced epithelial cell Golgi network association of wild-type bacteria, phenocopying the effect of null mutations of sseG or sseF. Binding of SseF to ACBD3 in infected cells required the presence of SseG. A single-amino-acid mutant of SseG and a double-amino-acid mutant of SseF were obtained that did not interact with ACBD3 in Saccharomyces cerevisiae. When either of these was produced together with the corresponding wild-type effector by Salmonella in infected cells, they enabled SCV-Golgi network association and interacted with ACBD3. However, these properties were lost and bacteria displayed an intracellular replication defect when cells were infected with Salmonella carrying both mutant genes. Knockdown of ACBD3 resulted in a replication defect of wild-type bacteria but did not further attenuate the growth defect of a ΔsseFG mutant strain. We propose a model in which interaction between SseF and SseG enables both proteins to bind ACBD3, thereby anchoring SCVs at the Golgi network and facilitating bacterial replication.

  • Journal article
    Cheverton AM, Gollan B, Przydacz M, Wong CT, Mylona A, Hare SA, Helaine Set al., 2016,

    A Salmonella Toxin Promotes Persister Formation through Acetylation of tRNA.

    , Molecular cell, Vol: 63, Pages: 86-96, ISSN: 1097-2765

    The recalcitrance of many bacterial infections to antibiotic treatment is thought to be due to the presence of persisters that are non-growing, antibiotic-insensitive cells. Eventually, persisters resume growth, accounting for relapses of infection. Salmonella is an important pathogen that causes disease through its ability to survive inside macrophages. After macrophage phagocytosis, a significant proportion of the Salmonella population forms non-growing persisters through the action of toxin-antitoxin modules. Here we reveal that one such toxin, TacT, is an acetyltransferase that blocks the primary amine group of amino acids on charged tRNA molecules, thereby inhibiting translation and promoting persister formation. Furthermore, we report the crystal structure of TacT and note unique structural features, including two positively charged surface patches that are essential for toxicity. Finally, we identify a detoxifying mechanism in Salmonella wherein peptidyl-tRNA hydrolase counteracts TacT-dependent growth arrest, explaining how bacterial persisters can resume growth.

  • Journal article
    Filloux A, Freemont P, 2016,

    Structural biology: baseplates in contractile machines

    , Nature Microbiology, Vol: 1, ISSN: 2058-5276
  • Journal article
    Taglialegna A, Navarro S, Ventura S, Garnett JA, Matthews S, Penades JR, Lasa I, Valle Jet al., 2016,

    Staphylococcal Bap Proteins Build Amyloid Scaffold Biofilm Matrices in Response to Environmental Signals

    , PLOS Pathogens, Vol: 12, ISSN: 1553-7366

    Biofilms are communities of bacteria that grow encased in an extracellular matrix that often contains proteins. The spatial organization and the molecular interactions between matrix scaffold proteins remain in most cases largely unknown. Here, we report that Bap protein of Staphylococcus aureus self-assembles into functional amyloid aggregates to build the biofilm matrix in response to environmental conditions. Specifically, Bap is processed and fragments containing at least the N-terminus of the protein become aggregation-prone and self-assemble into amyloid-like structures under acidic pHs and low concentrations of calcium. The molten globule-like state of Bap fragments is stabilized upon binding of the cation, hindering its self-assembly into amyloid fibers. These findings define a dual function for Bap, first as a sensor and then as a scaffold protein to promote biofilm development under specific environmental conditions. Since the pH-driven multicellular behavior mediated by Bap occurs in coagulase-negative staphylococci and many other bacteria exploit Bap-like proteins to build a biofilm matrix, the mechanism of amyloid-like aggregation described here may be widespread among pathogenic bacteria.

  • Journal article
    Willis A, Mazon-Moya M, Mostowy S, 2016,

    Investigation of septin biology in vivo using zebrafish.

    , Methods in Cell Biology, Vol: 136, Pages: 221-241, ISSN: 0091-679X

    The zebrafish (Danio rerio) is an important animal model to study cell biology in vivo. Benefits of the zebrafish include a fully annotated reference genome, an easily manipulable genome (for example, by morpholino oligonucleotide or CRISPR-Cas9), and transparent embryos for noninvasive, real-time microscopy using fluorescent transgenic lines. Zebrafish have orthologues of most human septins, and studies using larvae were used to investigate the role of septins in vertebrate development. The zebrafish larva is also an established model to study the cell biology of infection and has recently been used to visualize septin assembly during bacterial infection in vivo. Here, we describe protocols for the study of septins in zebrafish, with emphasis on techniques used to investigate the role of septins in host defense against bacterial infection.

  • Journal article
    Krokowski S, Mostowy S, 2016,

    Investigation of septins using infection by bacterial pathogens.

    , Methods in Cell Biology, Vol: 136, Pages: 117-134, ISSN: 0091-679X

    Investigation of the host cytoskeleton during infection by bacterial pathogens has significantly contributed to our understanding of cell biology and host defense. Work has shown that septins are recruited to the phagocytic cup as collarlike structures and enable bacterial entry into host cells. In the cytosol, septins can entrap actin-polymerizing bacteria in cage-like structures for targeting to autophagy, a highly conserved intracellular degradation process. In this chapter, we describe methods to investigate septin assembly and function during infection by bacterial pathogens. Use of these methods can lead to in-depth understanding of septin biology and suggest therapeutic approaches to combat infectious disease.

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