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1.
Downs Stephen G.; Ratnieks Francis L. W.; Badcock Nichola S.; Mynott Amanda 《Behavioral ecology》2001,12(1):47-50
Honeybee (Apis mellifera) colonies rob honey from each other
during periods of nectar shortage. Persistent robbing can killweak colonies. Primarily responsible for preventing robbingare guard bees. Previous research has shown that the probabilityof both nest mate and non-nest mate workers being acceptedby guards at the nest entrance increases as nectar availability
increases. The mechanism responsible for this change in guardacceptance can be explained by two competing hypotheses: OdorConvergence and Adaptive Threshold Shift. In this study wetested the Odor Convergence hypothesis. The acceptance by guardsat the nest entrance of workers transferred between four coloniesthat had been fed either odorless sucrose syrup (two colonies)or diluted heather honey (Calluna vulgaris) (two colonies)was measured for 3 days before feeding and during 2 weeks offeeding. Despite the large sample sizes, the probability ofguards accepting non-nest mates was not affected by the similaritiesor dissimilarities in food odor between guards' and non-nestmates' colonies. This finding contrasts with the accepted wisdom
that food odors are important in nest mate recognition in honeybeesand the data, therefore, strongly reject the Odor Convergencehypothesis. 相似文献
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Background
Protein translocation across the membrane of the Endoplasmic Reticulum (ER) is the first step in the biogenesis of secretory and membrane proteins. Proteins enter the ER by the Sec61 translocon, a proteinaceous channel composed of three subunits, α, β and γ. While it is known that Sec61α forms the actual channel, the function of the other two subunits remains to be characterized.Results
In the present study we have investigated the function of Sec61β in Drosophila melanogaster. We describe its role in the plasma membrane traffic of Gurken, the ligand for the Epidermal Growth Factor (EGF) receptor in the oocyte. Germline clones of the mutant allele of Sec61β show normal translocation of Gurken into the ER and transport to the Golgi complex, but further traffic to the plasma membrane is impeded. The defect in plasma membrane traffic due to absence of Sec61β is specific for Gurken and is not due to a general trafficking defect.Conclusion
Based on our study we conclude that Sec61β, which is part of the ER protein translocation channel affects a post-ER step during Gurken trafficking to the plasma membrane. We propose an additional role of Sec61β beyond protein translocation into the ER. 相似文献4.
Detection of attachment of enterotoxigenic Escherichia coli (ETEC) to human small intestinal cells by enzyme immunoassay 总被引:1,自引:0,他引:1
Tracey L. Mynott Richard K.J. Luke David S. Chandler 《FEMS immunology and medical microbiology》1995,10(3-4):207-218
Abstract Simple immunoassays were developed to study the binding between enterocytes of the small intestine and other cell types, and enterotoxigenic Escherichia coli (ETEC). CFA/I or CFA/II pilus protein or CFA-positive E. coli bacteria were wells of microtitre plates and incubated with vesicles or crude mucus prepared from human brush border enterocytes. Binding of the cell preparations was detected by adding specific rabbit anti-brush border IgG followed by urease-labelled goat anti-rabbit IgG and urea substrate. The binding of purified CFA/I to human or rabbit small intestine, human oral epithelial cells or Caco-2 cells was detected with specific anti-CFA/I IgG. Both human brush border and mucus-derived preparations were able to attach to ETEC. The binding was CFA-specific and strong enough to withstand several washings. In contrast, CFA/I did not bind to small intestinal cells of non-human small intestinal origin, indicating that there may be important differences in affinity between receptors present on human small intestinal cells and cells of non-human small intestinal origin. Antibodies directed against human small intestinal and non-small intestinal cells did not cross-react with either preparation, indicating that receptors between these different cell sources are different. The EIA proved useful during the identification of a newly-recognised 15 kDa bacterial surface component of ETEC strain H10407P, which may function as a putative attachment factor. The EIAs developed in this study were easy to perform and multiple tests could be performed on small samples, including biopsy samples obtained during endoscopy. 相似文献
5.
Sequence of a cDNA for mouse thymidylate synthase reveals striking similarity with the prokaryotic enzyme 总被引:11,自引:0,他引:11
Perryman SM; Rossana C; Deng TL; Vanin EF; Johnson LF 《Molecular biology and evolution》1986,3(4):313-321
We report the nucleotide sequence of a cloned cDNA, pMTS-3, that contains a
1-kb insert corresponding to mouse thymidylate synthase (E.C. 2.1.1.45).
The open reading frame of 921 nucleotides from the first AUG to the
termination codon specifies a protein with a molecular mass of 34,962
daltons. The predicted amino acid sequence is 90% identical with that of
the human enzyme. The mouse sequence also has an extremely high degree of
similarity (as much as 55% identity) with prokaryotic thymidylate synthase
sequences, indicating that thymidylate synthase is among the most highly
conserved proteins studied to date. The similarity is especially pronounced
(as much as 80% identity) in the 44-amino-acid region encompassing the
binding site for deoxyuridylic acid. The cDNA sequence also suggests that
mouse thymidylate synthase mRNA lacks a 3' untranslated region, since the
termination codon, UAA, is followed immediately by a poly(A) segment.
相似文献
6.
Littler DR Harrop SJ Brown LJ Pankhurst GJ Mynott AV Luciani P Mandyam RA Mazzanti M Tanda S Berryman MA Breit SN Curmi PM 《Proteins》2008,71(1):364-378
The crystal structures of two CLIC family members DmCLIC and EXC-4 from the invertebrates Drosophila melanogaster and Caenorhabditis elegans, respectively, have been determined. The proteins adopt a glutathione S-transferase (GST) fold. The structures are highly homologous to each other and more closely related to the known structures of the human CLIC1 and CLIC4 than to GSTs. The invertebrate CLICs show several unique features including an elongated C-terminal extension and a divalent metal binding site. The latter appears to alter the ancestral glutathione binding site, and thus, the invertebrate CLICs are unlikely to bind glutathione in the same manner as the GST proteins. Purified recombinant DmCLIC and EXC-4 both bind to lipid bilayers and can form ion channels in artificial lipid bilayers, albeit at low pH. EXC-4 differs from other CLIC proteins in that the conserved redox-active cysteine at the N-terminus of helix 1 is replaced by an aspartic acid residue. Other key distinguishing features of EXC-4 include the fact that it binds to artificial bilayers at neutral pH and this binding is not sensitive to oxidation. These differences with other CLIC family members are likely to be due to the substitution of the conserved cysteine by aspartic acid. 相似文献
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The preparation of a novel mononuclear complex of zirconium having an η8-bonded pentalene ligand and two η3-allyl groups is described. Its structure has been determined by 1H and 13C NMR spectroscopy. At room temperature some of the NMR signals are broadened, revealing that the compound is structurally dynamic. It is shown that the compound has C2 symmetry with the enantiomeric forms undergoing racemisation. 相似文献
9.
Brigida TL Lucena Billy M dos Santos João LS Moreira Ana Paula B Moreira Alvaro C Nunes Vasco Azevedo Anderson Miyoshi Fabiano L Thompson Marcos Antonio de MoraisJunior 《BMC microbiology》2010,10(1):298
Background
Bacteria may compete with yeast for nutrients during bioethanol production process, potentially causing economic losses. This is the first study aiming at the quantification and identification of Lactic Acid Bacteria (LAB) present in the bioethanol industrial processes in different distilleries of Brazil. 相似文献10.
Role of the reticulum in the stability and shape of the isolated human erythrocyte membrane 总被引:5,自引:7,他引:5 下载免费PDF全文
In order to examine the widely held hypothesis that the reticulum of proteins which covers the cytoplamsic surface of the human erythrocyte membrane controls cell stability and shape, we have assessed some of its properties. The reticulum, freed of the bilayer by extraction with Triton X-100, was found to be mechanically stable at physiological ionic strength but physically unstable at low ionic strength. The reticulum broke down after a characteristic lag period which decreased 500-fold between 0 degrees and 37 degrees C. The release of polypeptide band 4.1 from the reticulum preceded that of spectrin and actin, suggesting that band 4.1 might stabilize the ensemble but is not essential to its integrity. The time-course of breakdown was similar for ghosts, the reticulum inside of ghosts, and the isolated reticulum. However, at very low ionic strength, the reticulum was less stable within the ghost than when free; at higher ionic strength, the reverse was true. Over a wide range of conditions the membrane broke down to vesicles just as the reticulum disintegrated, presumably because the bilayer was mechanically stabilized by this network. The volume of both ghosts and naked reticula varied inversely and reversibly with ionic strength. The volume of the naked reticulum varied far more widely than the ghost, suggesting that its deformation was normally limited by the less extensible bilayer. The contour of the isolated reticulum was discoid and often dimpled or indented, as visualized in the fluorescence microscope after labeling of the ghosts with fluoroscein isothiocyanate. Reticula derived from ghosts which had lost the ability to crenate in isotonic saline were shriveled, even though the bilayer was smooth and expanded. Conversly, ghosts crenated by dinitrophenol yielded smooth, expanded reticula. We conclude that the reticulum is a durable, flexible, and elastic network which assumes and stabilizes the contour of the membrane but is not responsible for its crenation. 相似文献