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71.
Susanna KP Lau Rachel YY Fan Gilman KM Wong Jade LL Teng Kong-Hung Sze Herman Tse Kwok-Yung Yuen Patrick CY Woo 《Cell & Bioscience》2011,1(1):1-17
Background
Laribacter hongkongensis is a Gram-negative, sea gull-shaped rod associated with community-acquired gastroenteritis. The bacterium has been found in diverse freshwater environments including fish, frogs and drinking water reservoirs. Using the complete genome sequence data of L. hongkongensis, we performed a comprehensive analysis of putative transport-related genes and genes related to chemotaxis, motility and quorum sensing, which may help the bacterium adapt to the changing environments and combat harmful substances.Results
A genome-wide analysis using Transport Classification Database TCDB, similarity and keyword searches revealed the presence of a large diversity of transporters (n = 457) and genes related to chemotaxis (n = 52) and flagellar biosynthesis (n = 40) in the L. hongkongensis genome. The transporters included those from all seven major transporter categories, which may allow the uptake of essential nutrients or ions, and extrusion of metabolic end products and hazardous substances. L. hongkongensis is unique among closely related members of Neisseriaceae family in possessing higher number of proteins related to transport of ammonium, urea and dicarboxylate, which may reflect the importance of nitrogen and dicarboxylate metabolism in this assacharolytic bacterium. Structural modeling of two C4-dicarboxylate transporters showed that they possessed similar structures to the determined structures of other DctP-TRAP transporters, with one having an unusual disulfide bond. Diverse mechanisms for iron transport, including hemin transporters for iron acquisition from host proteins, were also identified. In addition to the chemotaxis and flagella-related genes, the L. hongkongensis genome also contained two copies of qseB/qseC homologues of the AI-3 quorum sensing system.Conclusions
The large number of diverse transporters and genes involved in chemotaxis, motility and quorum sensing suggested that the bacterium may utilize a complex system to adapt to different environments. Structural modeling will provide useful insights on the transporters in L. hongkongensis. 相似文献72.
The Nef protein is an important HIV virulence factor that promotes the degradation of host proteins to augment virus production and facilitate immune evasion. The best-characterized targets of Nef are major histocompatibility complex class I (MHC-I) and CD4, but Nef also has been reported to target several other proteins, including CD8β, CD28, CD80, CD86, and CD1d. To compare and contrast the effects of Nef on each protein, we constructed a panel of chimeric proteins in which the extracellular and transmembrane regions of the MHC-I allele HLA-A2 were fused to the cytoplasmic tails of CD4, CD28, CD8β, CD80, CD86, and CD1d. We found that Nef coprecipitated with and disrupted the expression of molecules with cytoplasmic tails from MHC-I HLA-A2, CD4, CD8β, and CD28, but Nef did not bind to or alter the expression of molecules with cytoplasmic tails from CD80, CD86, and CD1d. In addition, we used short interfering RNA (siRNA) knockdown and coprecipitation experiments to implicate AP-1 as a cellular cofactor for Nef in the downmodulation of both CD28 and CD8β. The interaction with AP-1 required for CD28 and CD8β differed from the AP-1 interaction required for MHC-I downmodulation in that it was mediated through the dileucine motif within Nef (LL(164,165)AA) and did not require the tyrosine binding pocket of the AP-1 μ subunit. In addition, we demonstrate a requirement for β-COP as a cellular cofactor for Nef that was necessary for the degradation of targeted molecules HLA-A2, CD4, and CD8. These studies provide important new information on the similarities and differences with which Nef affects intracellular trafficking and help focus future research on the best potential pharmaceutical targets. 相似文献
73.
Jessica L. Prince Daniel T. Claiborne Jonathan M. Carlson Malinda Schaefer Tianwei Yu Shabir Lahki Heather A. Prentice Ling Yue Sundaram A. Vishwanathan William Kilembe Paul Goepfert Matthew A. Price Jill Gilmour Joseph Mulenga Paul Farmer Cynthia A. Derdeyn Jiaming Tang David Heckerman Richard A. Kaslow Susan A. Allen Eric Hunter 《PLoS pathogens》2012,8(11)
74.
Loss of insect pollinators due to habitat fragmentation often results in negative effects on plant reproduction, but few studies
have simultaneously examined variation in the bee community, site characteristics and plant community characteristics to evaluate
their relative effects on plant reproduction in a fragmented habitat. We examined the reproduction of a common tallgrass prairie
forb, Amorpha canescens (Fabaceae), in large (>40 ha) and small (<2 ha) prairie remnants in Iowa and Minnesota in relation to the diversity and abundance
of its bee visitors, plant population size, and species density of the forb flowering community. We found significant positive
effects of the diversity of bees visiting A. canescens on percent fruit set at a site in both years of the study and in 2002 an additional significant positive effect of plant
species density. Abundance of bees visiting A. canescens had a significant positive effect on percent fruit set in 2002, but was only marginally significant in 2003. In 2003 but
not 2002, the plant species density at the sites had a significant negative effect on the diversity and abundance of bees
visiting A. canescens, indicating community-level characteristics can influence the bee community visiting any one species. Site size, a common predictor of plant reproduction in fragmented habitats did not contribute to any models of fruit set
and was only marginally related to bee diversity one year. Andrena quintilis, one of the three oligolectic bee species associated with A. canescens, was abundant at all sites, suggesting it has not been significantly affected by fragmentation. Our results show that the
diversity of bees visiting A. canescens is important for maintaining fruit set and that bee visitation is still sufficient for at least some fruit set in all populations,
suggesting these small remnants act as floral resource oases for bees in landscapes often dominated by agriculture. 相似文献
75.
The spores of Anabaena doliolum formed in light (light spores)and after transfer to darkness (dark spores) are biochemicallydifferent in that the light spores contain chlorophyll a andphycocyanin, while dark spores seem to lack them. The apparentbiosyntheses accompanying dark-spore germination seem to proceedin the following order: RNA, chlorophyll a, phycocyanin andDNA. Results of chloramphenicol treatment indicate that proteinsynthesis precedes RNA synthesis. The biosynthetic events followingRNA synthesis show a requirement for light. 相似文献
76.
Michael Tomasello Josep Call Katherine Nagell Raquel Olguin Malinda Carpenter 《Primates; journal of primatology》1994,35(2):137-154
Observations of chimpanzee gestural communication are reported. The observations represent the third longitudinal time point
of an ongoing study of the Yerkes Primate Center Field Station chimpanzee group. In contrast to observations at the first
two time points, the current observations are of a new generation of infants and juveniles. There were two questions. The
first concerned how young chimpanzees used their gestures, with special focus on the flexibility or intentionality displayed.
It was found that youngsters quite often used the same gesture in different contexts, and different gestures in the same context.
In addition, they sometimes used gestures in combinations in a single social encounter, these combinations did not convey
intentions that could not be conveyed by the component gestures, however. It was also found that individuals adjusted their
choice of signals depending on the attentional state of the recipient. The second question was how chimpanzees acquired their
gestural signals. In general, it was found that there was little consistency in the use of gestures among individuals, especially
for non-play gestures, with much individual variability both within and across generations. There were also a number of idiosyncratic
gestures used by single individuals at each time point. It was concluded from these results that youngsters were not imitatively
learning their communicatory gestures from conspecifics, but rather that they were individually conventionalizing them with
each other. Implications of these findings for the understanding of chimpanzee communication and social learning are discussed. 相似文献
77.
Evolutionary transfer of ORF-containing group I introns between different subcellular compartments (chloroplast and mitochondrion) 总被引:10,自引:2,他引:8
Turmel M; Cote V; Otis C; Mercier JP; Gray MW; Lonergan KM; Lemieux C 《Molecular biology and evolution》1995,12(4):533-545
We describe here a case of homologous introns containing homologous open
reading frames (ORFs) that are inserted at the same site in the large
subunit (LSU) rRNA gene of different organelles in distantly related
organisms. We show that the chloroplast LSU rRNA gene of the green alga
Chlamydomonas pallidostigmatica contains a group I intron (CpLSU.2)
encoding a site-specific endonuclease (I-CpaI). This intron is inserted at
the identical site (corresponding to position 1931-1932 of the Escherichia
coli 23S rRNA sequence) as a group I intron (AcLSU.m1) in the mitochondrial
LSU rRNA gene of the amoeboid protozoon Acanthamoeba castellanii. The
CpLSU.2 intron displays a remarkable degree of nucleotide similarity in
both primary sequence and secondary structure to the AcLSU.m1 intron;
moreover, the Acanthamoeba intron contains an ORF in the same location
within its secondary structure as the CpLSU.2 ORF and shares with it a
strikingly high level of amino acid similarity (65%; 42% identity). A
comprehensive survey of intron distribution at site 1931 of the chloroplast
LSU rRNA gene reveals a rather restricted occurrence within the
polyphyletic genus Chlamydomonas, with no evidence of this intron among a
number of non- Chlamydomonad green algae surveyed, nor in land plants. A
parallel survey of homologues of a previously described and similar
intron/ORF pair (C. reinhardtii chloroplast CrLSU/A. castellanii
mitochondrial AcLSU.m3) also shows a restricted occurrence of this intron
(site 2593) among chloroplasts, although the intron distribution is
somewhat broader than that observed at site 1931, with site-2593 introns
appearing in several green algal branches outside of the Chlamydomonas
lineage. The available data, while not definitive, are most consistent with
a relatively recent horizontal transfer of both site-1931 and site- 2593
introns (and their contained ORFs) between the chloroplast of a
Chlamydomonas-type organism and the mitochondrion of an Acanthamoeba- like
organism, probably in the direction chloroplast to mitochondrion. The data
also suggest that both introns could have been acquired in a single event.
相似文献
78.
79.
Background
Debates exist as to whether, as overall population health improves, the absolute and relative magnitude of income- and race/ethnicity-related health disparities necessarily increase—or derease. We accordingly decided to test the hypothesis that health inequities widen—or shrink—in a context of declining mortality rates, by examining annual US mortality data over a 42 year period.Methods and Findings
Using US county mortality data from 1960–2002 and county median family income data from the 1960–2000 decennial censuses, we analyzed the rates of premature mortality (deaths among persons under age 65) and infant death (deaths among persons under age 1) by quintiles of county median family income weighted by county population size. Between 1960 and 2002, as US premature mortality and infant death rates declined in all county income quintiles, socioeconomic and racial/ethnic inequities in premature mortality and infant death (both relative and absolute) shrank between 1966 and 1980, especially for US populations of color; thereafter, the relative health inequities widened and the absolute differences barely changed in magnitude. Had all persons experienced the same yearly age-specific premature mortality rates as the white population living in the highest income quintile, between 1960 and 2002, 14% of the white premature deaths and 30% of the premature deaths among populations of color would not have occurred.Conclusions
The observed trends refute arguments that health inequities inevitably widen—or shrink—as population health improves. Instead, the magnitude of health inequalities can fall or rise; it is our job to understand why. 相似文献80.
Disruption of steroid and prolactin receptor patterning in the mammary gland correlates with a block in lobuloalveolar development 总被引:8,自引:0,他引:8