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  • American Society for Microbiology  (14)
  • 1
    Online Resource
    Online Resource
    Structures of the Iron-Sulfur Flavoproteins from Methanosarcina thermophila and Archaeoglobus fulgidus
    American Society for Microbiology ; 2005
    In:  Journal of Bacteriology Vol. 187, No. 11 ( 2005-06), p. 3848-3854
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 187, No. 11 ( 2005-06), p. 3848-3854
    Abstract: Iron-sulfur flavoproteins (ISF) constitute a widespread family of redox-active proteins in anaerobic prokaryotes. Based on sequence homologies, their overall structure is expected to be similar to that of flavodoxins, but in addition to a flavin mononucleotide cofactor they also contain a cubane-type [4Fe:4S] cluster. In order to gain further insight into the function and properties of ISF, the three-dimensional structures of two ISF homologs, one from the thermophilic methanogen Methanosarcina thermophila and one from the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus , were determined. The structures indicate that ISF assembles to form a tetramer and that electron transfer between the two types of redox cofactors requires oligomerization to juxtapose the flavin mononucleotide and [4Fe:4S] cluster bound to different subunits. This is only possible between different monomers upon oligomerization. Fundamental differences in the surface properties of the two ISF homologs underscore the diversity encountered within this protein family.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.187.11.3848-3854.2005
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Mycobacterium marinum Erp Is a Virulence Determinant Required for Cell Wall Integrity and Intracellular Survival
    American Society for Microbiology ; 2006
    In:  Infection and Immunity Vol. 74, No. 6 ( 2006-06), p. 3125-3133
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 74, No. 6 ( 2006-06), p. 3125-3133
    Abstract: The Mycobacterium tuberculosis exported repetitive protein (Erp) is a virulence determinant required for growth in cultured macrophages and in vivo. To better understand the role of Erp in Mycobacterium pathogenesis, we generated a mutation in the erp homologue of Mycobacterium marinum , a close genetic relative of M. tuberculosis. erp -deficient M. marinum was growth attenuated in cultured macrophage monolayers and during chronic granulomatous infection of leopard frogs, suggesting that Erp function is similarly required for the virulence of both M. tuberculosis and M. marinum . To pinpoint the step in infection at which Erp is required, we utilized a zebrafish embryo infection model that allows M. marinum infections to be visualized in real-time, comparing the erp -deficient strain to a ΔRD1 mutant whose stage of attenuation was previously characterized in zebrafish embryos. A detailed microscopic examination of infected embryos revealed that bacteria lacking Erp were compromised very early in infection, failing to grow and/or survive upon phagocytosis by host macrophages. In contrast, ΔRD1 mutant bacteria grow normally in macrophages but fail to induce host macrophage aggregation and subsequent cell-to-cell spread. Consistent with these in vivo findings, erp -deficient but not RD1-deficient bacteria exhibited permeability defects in vitro, which may be responsible for their specific failure to survive in host macrophages.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.02061-05
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1483247-1
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  • 3
    Online Resource
    Online Resource
    Multiple structural proteins are required for both transcriptional activation and negative autoregulation of Caulobacter crescentus flagellar genes
    American Society for Microbiology ; 1994
    In:  Journal of Bacteriology Vol. 176, No. 24 ( 1994-12), p. 7587-7600
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 176, No. 24 ( 1994-12), p. 7587-7600
    Abstract: The periodic and sequential expression of flagellar (fla) genes in the Caulobacter crescentus cell cycle depends on their organization into levels I to IV of a regulatory hierarchy in which genes at the top of the hierarchy are expressed early in the cell cycle and are required for the later expression of genes below them. In these studies, we have examined the regulatory role of level II fliF operon, which is located near the top of the hierarchy. The last gene in the fliF operon, flbD, encodes a transcriptional factor required for activation of sigma 54-dependent promoters at levels III and IV and negative autoregulation of the level II fliF promoter. We have physically mapped the fliF operon, identified four new genes in the transcription unit, and determined that the organization of these genes is 5'-fliF-fliG-flbE-fliN-flbD-3'. Three of the genes encode homologs of the MS ring protein (FliF) and two switch proteins (FliG and FliN) of enteric bacteria, and the fourth encodes a predicted protein (FlbE) without obvious similarities to known bacterial proteins. We have introduced nonpolar mutations in each of the open reading frames and shown that all of the newly identified genes (fliF, fliG, flbE, and fliN) are required in addition to flbD for activation of the sigma 54-dependent flgK and flbG promoters at level III. In contrast, fliF, fliG, and flbE, but not fliN, are required in addition to flbD for negative autoregulation of the level II fliF promoter. The simplest interpretation of these results is that the requirements of FlbD in transcriptional activation and repression are not identical, and we speculate that FlbD function is subject to dual or overlapping controls. We also discuss the requirement of multiple structural genes for regulation of levels II and III genes and suggest that fla gene expression in C. crescentus may be coupled to two checkpoints in flagellum assembly.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/jb.176.24.7587-7600.1994
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1994
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Enhanced Immunogenicity and Protective Efficacy of a Campylobacter jejuni Conjugate Vaccine Coadministered with Liposomes Containing Monophosphoryl Lipid A and QS-21
    American Society for Microbiology ; 2019
    In:  mSphere Vol. 4, No. 3 ( 2019-06-26)
    Details
    In: mSphere, American Society for Microbiology, Vol. 4, No. 3 ( 2019-06-26)
    Abstract: Campylobacter jejuni is among the most common causes of diarrheal disease worldwide and efforts to develop protective measures against the pathogen are ongoing. One of the few defined virulence factors targeted for vaccine development is the capsule polysaccharide (CPS). We have developed a capsule conjugate vaccine against C. jejuni strain 81-176 (CPS-CRM) that is immunogenic in mice and nonhuman primates (NHPs) but only moderately immunogenic in humans when delivered alone or with aluminum hydroxide. To enhance immunogenicity, two novel liposome-based adjuvant systems, the Army Liposome Formulation (ALF), containing synthetic monophosphoryl lipid A, and ALF plus QS-21 (ALFQ), were evaluated with CPS-CRM in this study. In mice, ALF and ALFQ induced similar amounts of CPS-specific IgG that was significantly higher than levels induced by CPS-CRM alone. Qualitative differences in antibody responses were observed where CPS-CRM alone induced Th2-biased IgG1, whereas ALF and ALFQ enhanced Th1-mediated anti-CPS IgG2b and IgG2c and generated functional bactericidal antibody titers. CPS-CRM + ALFQ was superior to vaccine alone or CPS-CRM + ALF in augmenting antigen-specific Th1, Th2, and Th17 cytokine responses and a significantly higher proportion of CD4 + IFN-γ + IL-2 + TNF-α + and CD4 + IL-4 + IL-10 + T cells. ALFQ also significantly enhanced anti-CPS responses in NHPs when delivered with CPS-CRM compared to alum- or ALF-adjuvanted groups and showed the highest protective efficacy against diarrhea following orogastric challenge with C. jejuni . This study provides evidence that the ALF adjuvants may provide enhanced immunogenicity of this and other novel C. jejuni capsule conjugate vaccines in humans. IMPORTANCE Campylobacter jejuni is a leading cause of diarrheal disease worldwide, and currently no preventative interventions are available. C. jejuni is an invasive mucosal pathogen that has a variety of polysaccharide structures on its surface, including a capsule. In phase 1 studies, a C. jejuni capsule conjugate vaccine was safe but poorly immunogenic when delivered alone or with aluminum hydroxide. Here, we report enhanced immunogenicity of the conjugate vaccine delivered with liposome adjuvants containing monophosphoryl lipid A without or with QS-21, known as ALF and ALFQ, respectively, in preclinical studies. Both liposome adjuvants significantly enhanced immunity in mice and nonhuman primates and improved protective efficacy of the vaccine compared to alum in a nonhuman primate C. jejuni diarrhea model, providing promising evidence that these potent adjuvant formulations may enhance immunogenicity in upcoming human studies with this C. jejuni conjugate and other malaria and HIV vaccine platforms.
    Type of Medium: Online Resource
    ISSN: 2379-5042
    URL: Article
    DOI: 10.1128/mSphere.00101-19
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2019
    detail.hit.zdb_id: 2844248-9
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  • 5
    Online Resource
    Online Resource
    A crtB homolog essential for photochromogenicity in Mycobacterium marinum: isolation, characterization, and gene disruption via homologous recombination
    American Society for Microbiology ; 1997
    In:  Journal of Bacteriology Vol. 179, No. 18 ( 1997-09), p. 5862-5868
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 179, No. 18 ( 1997-09), p. 5862-5868
    Abstract: A gene essential for light-induced pigment production was isolated from the photochromogen Mycobacterium marinum by heterologous complementation of an M. marinum cosmid library in the nonchromogen Mycobacterium smegmatis. This gene is part of an operon and homologous to the Streptomyces griseus and Myxococcus xanthus crtB genes encoding phytoene synthase. Gene replacement at this locus was achieved via homologous recombination, demonstrating that its expression is essential for photochromogenicity. The ease of targeted gene disruption in this pathogenic Mycobacterium allows for the dissection of the molecular basis of mycobacterial pathogenesis.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/jb.179.18.5862-5868.1997
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1997
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Mycobacterium marinum causes both long-term subclinical infection and acute disease in the leopard frog (Rana pipiens)
    American Society for Microbiology ; 1997
    In:  Infection and Immunity Vol. 65, No. 2 ( 1997-02), p. 767-773
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 65, No. 2 ( 1997-02), p. 767-773
    Abstract: Mycobacterium marinum grows at an optimal temperature of 33 degrees C, far lower than that for M. tuberculosis. Consequently, M. marinum infection of mammals is restricted largely to the cooler surfaces of the body, such as the extremities, but it causes a systemic infection in a large number of poikilothermic animals. Here, we describe a laboratory animal model for M. marinum disease in the leopard frog (Rana pipiens), a natural host species. M. marinum causes a chronic granulomatous, nonlethal disease in immunocompetent frogs. Immunosuppression of the frogs with hydrocortisone results in an acute, fulminant, lethal disease. This animal model, in which a spectrum of tuberculosis-like disease can be produced, will be useful for the dissection of the genetic basis of mycobacterial pathogenesis.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/iai.65.2.767-773.1997
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1997
    detail.hit.zdb_id: 1483247-1
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  • 7
    Online Resource
    Online Resource
    Hepatitis B Virus X Protein Function Requires Zinc Binding
    American Society for Microbiology ; 2019
    In:  Journal of Virology Vol. 93, No. 16 ( 2019-08-15)
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 93, No. 16 ( 2019-08-15)
    Abstract: The host structural maintenance of chromosomes 5/6 complex (Smc5/6) suppresses hepatitis B virus (HBV) transcription. HBV counters this restriction by expressing the X protein (HBx), which redirects the cellular DNA damage-binding protein 1 (DDB1)-containing E3 ubiquitin ligase to target Smc5/6 for degradation. However, the details of how HBx modulates the interaction between DDB1 and Smc5/6 remain to be determined. In this study, we performed biophysical analyses of recombinant HBx and functional analysis of HBx mutants in HBV-infected primary human hepatocytes (PHH) to identify key regions and residues that are required for HBx function. We determined that recombinant HBx is soluble and exhibits stoichiometric zinc binding when expressed in the presence of DDB1. Mass spectrometry-based hydrogen-deuterium exchange and cysteine-specific chemical footprinting of the HBx:DDB1 complex identified several HBx cysteine residues (located between amino acids 61 and 137) that are likely involved in zinc binding. These cysteine residues did not form disulfide bonds in HBx expressed in human cells. In line with the biophysical data, functional analysis demonstrated that HBx amino acids 45 to 140 are required for Smc6 degradation and HBV transcription in PHH. Furthermore, site-directed mutagenesis determined that C61, C69, C137, and H139 are necessary for HBx function, although they are likely not essential for DDB1 binding. This CCCH motif is highly conserved in HBV as well as in the X proteins from various mammalian hepadnaviruses. Collectively, our data indicate that the essential HBx cysteine and histidine residues form a zinc-binding motif that is required for HBx function. IMPORTANCE The structural maintenance of chromosomes 5/6 complex (Smc5/6) is a host restriction factor that suppresses HBV transcription. HBV counters this restriction by expressing HBV X protein (HBx), which redirects a host ubiquitin ligase to target Smc5/6 for degradation. Despite this recent advance in understanding HBx function, the key regions and residues of HBx required for Smc5/6 degradation have not been determined. In the present study, we performed biochemical, biophysical, and cell-based analyses of HBx. By doing so, we mapped the minimal functional region of HBx and identified a highly conserved CCCH motif in HBx that is likely responsible for coordinating zinc and is essential for HBx function. We also developed a method to produce soluble recombinant HBx protein that likely adopts a physiologically relevant conformation. Collectively, this study provides new insights into the HBx structure-function relationship and suggests a new approach for structural studies of this enigmatic viral regulatory protein.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.00250-19
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2019
    detail.hit.zdb_id: 1495529-5
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  • 8
    Online Resource
    Online Resource
    Fimbrial Typing of Bordetella pertussis Isolates: Agglutination with Polyclonal and Monoclonal Antibodies
    American Society for Microbiology ; 2001
    In:  Journal of Clinical Microbiology Vol. 39, No. 11 ( 2001-11), p. 4220-4220
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 39, No. 11 ( 2001-11), p. 4220-4220
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.39.11.4220.2001
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    Erratum for Ramakrishnan et al., “Enhanced Immunogenicity and Protective Efficacy of a Campylobacter jejuni Conjugate Vaccine Coadministered with Liposomes Containing Monophosphoryl Lipid A and QS-21”
    American Society for Microbiology ; 2019
    In:  mSphere Vol. 4, No. 3 ( 2019-06-26)
    Details
    In: mSphere, American Society for Microbiology, Vol. 4, No. 3 ( 2019-06-26)
    Type of Medium: Online Resource
    ISSN: 2379-5042
    URL: Article
    DOI: 10.1128/mSphere.00440-19
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2019
    detail.hit.zdb_id: 2844248-9
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  • 10
    Online Resource
    Online Resource
    Transcription Repressor Protein ZBTB25 Associates with HDAC1-Sin3a Complex in Mycobacterium tuberculosis-Infected Macrophages, and Its Inhibition Clears Pathogen by Autophagy
    American Society for Microbiology ; 2021
    In:  mSphere Vol. 6, No. 1 ( 2021-02-24)
    Details
    In: mSphere, American Society for Microbiology, Vol. 6, No. 1 ( 2021-02-24)
    Abstract: Downregulation of host gene expression is a key strategy employed by intracellular pathogens for their survival in macrophages and subsequent pathogenesis. In a previous study, we have shown that histone deacetylase 1 (HDAC1) levels go up in macrophages infected with Mycobacterium tuberculosis , and it hypoacetylates histone H3 at the promoter of IL-12B gene, leading to its downregulation. We now show that after infection with M. tuberculosis , HDAC1 is phosphorylated, and the levels of phosphorylated HDAC1 (pHDAC1) increase significantly in macrophages. We found that transcriptional repressor protein zinc finger and BTB domain 25 (ZBTB25) and transcriptional corepressor Sin3a associate with the HDAC1 silencing complex, which is recruited to the promoter of IL-12B to downregulate its expression in infected macrophages. Knocking down of ZBTB25 enhanced release of IL-12p40 from infected macrophages. Inhibition of HDAC1 and ZBTB25 promoted colocalization of M. tuberculosis and LC3 (microtubule-associated protein 1A/1B-light chain 3) in autophagosomes. Induction of autophagy resulted in the killing of intracellular M. tuberculosis . Enhanced phosphorylation of JAK2 and STAT4 was observed in macrophages upon treatment with HDAC1 and ZBTB inhibitors, and inhibition of JAK2/STAT4 negated the killing of the intracellular pathogen, suggesting their role in the autophagy-mediated killing of intracellular M. tuberculosis . In view of the emergence of drug resistance in M. tuberculosis , host-directed therapy is an attractive alternative strategy to combat tuberculosis (TB). HDACs have been proposed to be host targets for TB treatment. Our study indicates that ZBTB25, a functional subunit of the HDAC1/Sin3a repressor complex involved in IL-12B suppression, could be an alternative target for host-directed anti-TB therapy. IMPORTANCE Following infection with M. tuberculosis , levels of HDAC1 go up in macrophages, and it is recruited to the promoter of IL-12B where it hypoacetylates histone H3, leading to the downregulation of the gene. Here, we show that host transcriptional repressor protein ZBTB25 and transcriptional corepressor Sin3a associate with HDAC1 in the silencing complex. Knocking down of ZBTB25 prevented the recruitment of the complex to the promoter and consequently enhanced the gene expression and the release of IL-12p40 from infected macrophages. Pharmacological inhibition of ZBTB25 in infected macrophages resulted in the induction of autophagy and killing of intracellular M. tuberculosis . Drug-resistant TB is a serious challenge to TB control programs all over the world which calls for finding alternative therapeutic methods. Host-directed therapy is gaining significant momentum in treating infectious diseases. We propose that ZBTB25 is a potential target for host-directed treatment of TB.
    Type of Medium: Online Resource
    ISSN: 2379-5042
    URL: Article
    DOI: 10.1128/mSphere.00036-21
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2021
    detail.hit.zdb_id: 2844248-9
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