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Search Results: 1 - 10 of 203256 matches for " Roslyn N. Brown "
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Top-Down Characterization of the Post-Translationally Modified Intact Periplasmic Proteome from the Bacterium Novosphingobium aromaticivorans
Si Wu,Roslyn N. Brown,Samuel H. Payne,Da Meng
International Journal of Proteomics , 2013, DOI: 10.1155/2013/279590
Abstract:
Diverse Secreted Effectors Are Required for Salmonella Persistence in a Mouse Infection Model
Afshan S. Kidwai, Ivy Mushamiri, George S. Niemann, Roslyn N. Brown, Joshua N. Adkins, Fred Heffron
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070753
Abstract: Salmonella enterica serovar Typhimurium causes typhoid-like disease in mice and is a model of typhoid fever in humans. One of the hallmarks of typhoid is persistence, the ability of the bacteria to survive in the host weeks after infection. Virulence factors called effectors facilitate this process by direct transfer to the cytoplasm of infected cells thereby subverting cellular processes. Secretion of effectors to the cell cytoplasm takes place through multiple routes, including two separate type III secretion (T3SS) apparati as well as outer membrane vesicles. The two T3SS are encoded on separate pathogenicity islands, SPI-1 and -2, with SPI-1 more strongly associated with the intestinal phase of infection, and SPI-2 with the systemic phase. Both T3SS are required for persistence, but the effectors required have not been systematically evaluated. In this study, mutations in 48 described effectors were tested for persistence. We replaced each effector with a specific DNA barcode sequence by allelic exchange and co-infected with a wild-type reference to calculate the ratio of wild-type parent to mutant at different times after infection. The competitive index (CI) was determined by quantitative PCR in which primers that correspond to the barcode were used for amplification. Mutations in all but seven effectors reduced persistence demonstrating that most effectors were required. One exception was CigR, a recently discovered effector that is widely conserved throughout enteric bacteria. Deletion of cigR increased lethality, suggesting that it may be an anti-virulence factor. The fact that almost all Salmonella effectors are required for persistence argues against redundant functions. This is different from effector repertoires in other intracellular pathogens such as Legionella.
A Comprehensive Subcellular Proteomic Survey of Salmonella Grown under Phagosome-Mimicking versus Standard Laboratory Conditions
Roslyn N. Brown,James A. Sanford,Jea H. Park,Brooke L. Deatherage,Boyd L. Champion,Richard D. Smith,Fred Heffron,Joshua N. Adkins
International Journal of Proteomics , 2012, DOI: 10.1155/2012/123076
Abstract: Towards developing a systems-level pathobiological understanding of Salmonella enterica, we performed a subcellular proteomic analysis of this pathogen grown under standard laboratory and phagosome-mimicking conditions in vitro. Analysis of proteins from cytoplasmic, inner membrane, periplasmic, and outer membrane fractions yielded coverage of 25% of the theoretical proteome. Confident subcellular location could be assigned to over 1000 proteins, with good agreement between experimentally observed location and predicted/known protein properties. Comparison of protein location under the different environmental conditions provided insight into dynamic protein localization and possible moonlighting (multiple function) activities. Notable examples of dynamic localization were the response regulators of two-component regulatory systems (e.g., ArcB and PhoQ). The DNA-binding protein Dps that is generally regarded as cytoplasmic was significantly enriched in the outer membrane for all growth conditions examined, suggestive of moonlighting activities. These observations imply the existence of unknown transport mechanisms and novel functions for a subset of Salmonella proteins. Overall, this work provides a catalog of experimentally verified subcellular protein locations for Salmonella and a framework for further investigations using computational modeling. 1. Introduction The pursuit of a systems-level understanding of bacterial physiology requires not only knowledge about the identity, function, and relative abundance of proteins, but also insight into the subcellular localization of these proteins. Subcellular protein localization is linked to protein function, potential protein-protein interactions, and to interactions between a cell and its exterior environment. The observation of proteins in unexpected cellular compartments gives clues about the presence of possible alternate functions. Hence, there is a growing appreciation for the presence of bacterial “moonlighting proteins,” that is, those proteins that have a secondary function depending on subcellular location [1–3]. Experimentally verified localization also provides a foundation for describing proteins that are “hypothetical,” uncharacterized, or that contain domains of unknown function. Furthermore, with the increasing use of systems biology approaches, including genome-scale models of metabolism [4] and regulation to study microbial functions, experimentally founded protein localization on a global scale is necessary to produce more accurate model constraints. Subcellular proteomics has emerged as
Genome-Scale Modeling of Light-Driven Reductant Partitioning and Carbon Fluxes in Diazotrophic Unicellular Cyanobacterium Cyanothece sp. ATCC 51142
Trang T. Vu ,Sergey M. Stolyar ,Grigoriy E. Pinchuk,Eric A. Hill,Leo A. Kucek,Roslyn N. Brown,Mary S. Lipton,Andrei Osterman,Jim K. Fredrickson,Allan E. Konopka,Alexander S. Beliaev ,Jennifer L. Reed
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002460
Abstract: Genome-scale metabolic models have proven useful for answering fundamental questions about metabolic capabilities of a variety of microorganisms, as well as informing their metabolic engineering. However, only a few models are available for oxygenic photosynthetic microorganisms, particularly in cyanobacteria in which photosynthetic and respiratory electron transport chains (ETC) share components. We addressed the complexity of cyanobacterial ETC by developing a genome-scale model for the diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142. The resulting metabolic reconstruction, iCce806, consists of 806 genes associated with 667 metabolic reactions and includes a detailed representation of the ETC and a biomass equation based on experimental measurements. Both computational and experimental approaches were used to investigate light-driven metabolism in Cyanothece sp. ATCC 51142, with a particular focus on reductant production and partitioning within the ETC. The simulation results suggest that growth and metabolic flux distributions are substantially impacted by the relative amounts of light going into the individual photosystems. When growth is limited by the flux through photosystem I, terminal respiratory oxidases are predicted to be an important mechanism for removing excess reductant. Similarly, under photosystem II flux limitation, excess electron carriers must be removed via cyclic electron transport. Furthermore, in silico calculations were in good quantitative agreement with the measured growth rates whereas predictions of reaction usage were qualitatively consistent with protein and mRNA expression data, which we used to further improve the resolution of intracellular flux values.
Top-Down Characterization of the Post-Translationally Modified Intact Periplasmic Proteome from the Bacterium Novosphingobium aromaticivorans
Si Wu,Roslyn N. Brown,Samuel H. Payne,Da Meng,Rui Zhao,Nikola Toli?,Li Cao,Anil Shukla,Matthew E. Monroe,Ronald J. Moore,Mary S. Lipton,Ljiljana Pa?a-Toli?
International Journal of Proteomics , 2013, DOI: 10.1155/2013/279590
Abstract: The periplasm of Gram-negative bacteria is a dynamic and physiologically important subcellular compartment where the constant exposure to potential environmental insults amplifies the need for proper protein folding and modifications. Top-down proteomics analysis of the periplasmic fraction at the intact protein level provides unrestricted characterization and annotation of the periplasmic proteome, including the post-translational modifications (PTMs) on these proteins. Here, we used single-dimension ultra-high pressure liquid chromatography coupled with the Fourier transform mass spectrometry (FTMS) to investigate the intact periplasmic proteome of Novosphingobium aromaticivorans. Our top-down analysis provided the confident identification of 55 proteins in the periplasm and characterized their PTMs including signal peptide removal, N-terminal methionine excision, acetylation, glutathionylation, pyroglutamate, and disulfide bond formation. This study provides the first experimental evidence for the expression and periplasmic localization of many hypothetical and uncharacterized proteins and the first unrestrictive, large-scale data on PTMs in the bacterial periplasm. 1. Introduction The periplasm of Gram-negative bacteria is a hydrated gel located between the cytoplasmic and outer membranes and is comprised of peptidoglycan (cell wall), proteins, carbohydrates, and small solutes [1–3]. The periplasm is a dynamic subcellular compartment important for trafficking of molecules into and out of cells, maintaining cellular osmotic balance, envelope structure, responding to environmental cues and stresses, electron transport, xenobiotic metabolism, and protein folding and modification [4]. The periplasm provides a good model system to study protein biogenesis, composition, sorting, and modification at the molecular level. Indeed, it is analogous in many ways to the endoplasmic reticulum of eukaryotic cells in terms of transport, folding, and quality control [3]. Localization to the periplasm and beyond often involves an N-terminal secretion signal that targets the protein for translocation across the cytoplasmic membrane via the general secretory pathway [5]. These secretion signals (also known as signal peptides) are cleaved by signal peptidases located in the cytoplasmic membrane [6]. Thus, it is expected that signal peptide cleavage is a common modification in the periplasmic proteome. Compared to the cytoplasm, the periplasm is more vulnerable to changes in pH, temperature, and osmolarity in the external environment [4, 7, 8]. For structural stability in
A Metapopulation Model of Tuberculosis Transmission with a Case Study from High to Low Burden Areas
Roslyn I. Hickson, Geoffry N. Mercer, Kamalini M. Lokuge
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034411
Abstract: Tuberculosis (TB) is a growing problem worldwide, especially with the emergence and high prevalence of multidrug-resistant strains. We develop a metapopulation model for TB spread, which is particularly suited to investigating transmission between areas of high and low prevalence. A case study of cross-border transmission in the Torres Strait region of Australia and Papua New Guinea (PNG) is considered and a sensitivity analysis is conducted. We find that only 6 of the 50 parameters analysed are important to the cumulative number of clinically active TB patients in the entire region. Of these, only the detection rate in PNG is found to be an important intervention parameter. We therefore give insight into the extent the area with the high burden of TB (PNG in the case study) is dominating the TB dynamics of the entire region. Furthermore, the sensitivity analysis results give insight into the data that most important to collect and refine, which is found to be data relating to the PNG parameters.
Singleness, Marriage, and the Construction of Heterosexual Masculinities: Australian Men Teaching English in Japan
Roslyn Appleby
PORTAL : Journal of Multidisciplinary International Studies , 2013,
Abstract: This article reports on a study of Australian men and their accounts of living and working in Japan as English language teachers. In this site, recent research has explored Japanese discourses of desire for the West, Western men, and English language learning. These patterns of desire have afforded white Western men a privileged personal and professional status in Japan, and enabled access to employment opportunities as teachers of English language. At the same time, white Western men working as English language teachers face the challenge of negotiating competing discourses that threaten their social status. In particular, their employment in a lowly-regarded profession and a reputation for sexual promiscuity potentially position Western male language teachers as the ‘white trash’ of Asia. My analysis of interview data focuses on the ways in which the men negotiate these discourses, and construct ‘respectable’ Western heterosexual masculinities by mobilising a binary distinction between singleness and marriage. Marriage to a Japanese spouse is presented as a bulwark against alignment with problematic discourses that threaten the status of white masculinity: it is associated with fidelity and maturity, and with integration into Japanese social, linguistic and professional communities. However, the articulation of marital status also reinforces a marginalised position for teachers who do not conform to heteronormative expectations.
‘A Bit of a Grope’: Gender, Sex and Racial Boundaries in Transitional East Timor
Roslyn Appleby
PORTAL : Journal of Multidisciplinary International Studies , 2010,
Abstract: This paper considers the gender positioning of white Australian women working on aid projects in East Timor during the military and aid intervention of 2000-2002. Drawing on interviews with women employed in English language teaching programs, I compare the positions women adopted in relation to their engagement with men in the foreign intervention/occupation community and with men in the local Timorese community. From the women’s perspective, the intervention was constructed as patriarchal regime that carried the gendered legacy of an earlier colonial era. This context provided a challenging domain for women development workers, as they juggled often conflicting discourses of gender equality and cultural sensitivity in their relations with men in the community of foreign occupiers, and with local Timorese men. The women’s self positioning in relation to these two groups varied markedly: while they readily rejected the behaviour and attitudes of foreign men as sexist and patriarchal, their response to Timorese men was more complex and ambivalent, demonstrating an awareness of their own inappropriacy as foreign intruders in this space.
Fitness and Physical Activity in Children and Youth with Disabilities
Maria A. Fragala-Pinkham,Margaret E. O'Neil,Kristie F. Bjornson,Roslyn N. Boyd
International Journal of Pediatrics , 2012, DOI: 10.1155/2012/162648
Abstract:
Fitness and Physical Activity in Children and Youth with Disabilities
Maria A. Fragala-Pinkham,Margaret E. O'Neil,Kristie F. Bjornson,Roslyn N. Boyd
International Journal of Pediatrics , 2012, DOI: 10.1155/2012/162648
Abstract:
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