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61.
Yildirim S Lin W Hitchins AD Jaykus LA Altermann E Klaenhammer TR Kathariou S 《Applied and environmental microbiology》2004,70(7):4158-4164
Listeria monocytogenes contamination of ready-to-eat foods has been implicated in numerous outbreaks of food-borne listeriosis. However, the health hazards posed by L. monocytogenes detected in foods may vary, and speculations exist that strains actually implicated in illness may constitute only a fraction of those that contaminate foods. In this study, examination of 34 serogroup 4 (putative or confirmed serotype 4b) isolates of L. monocytogenes obtained from various foods and food-processing environments, without known implication in illness, revealed that many of these strains had methylation of cytosines at GATC sites in the genome, rendering their DNA resistant to digestion by the restriction endonuclease Sau3AI. These strains also harbored a gene cassette with putative restriction-modification system genes as well as other, genomically unlinked genetic markers characteristic of the major epidemic-associated lineage of L. monocytogenes (epidemic clone I), implicated in numerous outbreaks in Europe and North America. This may reflect a relatively high fitness of strains with these genetic markers in foods and food-related environments relative to other serotype 4b strains and may partially account for the repeated involvement of such strains in human food-borne listeriosis. 相似文献
62.
Embryonic stem cells: staying plastic on plastic 总被引:1,自引:0,他引:1
63.
The THAP domain: a novel protein motif with similarity to the DNA-binding domain of P element transposase 总被引:5,自引:0,他引:5
Roussigne M Kossida S Lavigne AC Clouaire T Ecochard V Glories A Amalric F Girard JP 《Trends in biochemical sciences》2003,28(2):66-69
We have identified a novel evolutionarily conserved protein motif - designated the THAP domain - that defines a new family of cellular factors. We have found that the THAP domain presents striking similarities with the site-specific DNA-binding domain (DBD) of Drosophila P element transposase, including a similar size, N-terminal location, and conservation of the residues that define the THAP motif, such as the C2CH signature (Cys-Xaa(2-4)-Cys-Xaa(35-50)-Cys-Xaa(2)-His). Our results suggest that the THAP domain is a novel example of a DBD that is shared between cellular proteins and transposases from mobile genomic parasites. 相似文献
64.
65.
Progress in the development of a recombinant vaccine for human hookworm disease: the Human Hookworm Vaccine Initiative 总被引:11,自引:0,他引:11
Hotez PJ Zhan B Bethony JM Loukas A Williamson A Goud GN Hawdon JM Dobardzic A Dobardzic R Ghosh K Bottazzi ME Mendez S Zook B Wang Y Liu S Essiet-Gibson I Chung-Debose S Xiao S Knox D Meagher M Inan M Correa-Oliveira R Vilk P Shepherd HR Brandt W Russell PK 《International journal for parasitology》2003,33(11):1245-1258
Hookworm infection is one of the most important parasitic infections of humans, possibly outranked only by malaria as a cause of misery and suffering. An estimated 1.2 billion people are infected with hookworm in areas of rural poverty in the tropics and subtropics. Epidemiological data collected in China, Southeast Asia and Brazil indicate that, unlike other soil-transmitted helminth infections, the highest hookworm burdens typically occur in adult populations, including the elderly. Emerging data on the host cellular immune responses of chronically infected populations suggest that hookworms induce a state of host anergy and immune hyporesponsiveness. These features account for the high rates of hookworm reinfection following treatment with anthelminthic drugs and therefore, the failure of anthelminthics to control hookworm. Despite the inability of the human host to develop naturally acquired immune responses to hookworm, there is evidence for the feasibility of developing a vaccine based on the successes of immunising laboratory animals with either attenuated larval vaccines or antigens extracted from the alimentary canal of adult blood-feeding stages. The major antigens associated with each of these larval and adult hookworm vaccines have been cloned and expressed in prokaryotic and eukaryotic systems. However, only eukaryotic expression systems (e.g., yeast, baculovirus, and insect cells) produce recombinant proteins that immunologically resemble the corresponding native antigens. A challenge for vaccinologists is to formulate selected eukaryotic antigens with appropriate adjuvants in order to elicit high antibody titres. In some cases, antigen-specific IgE responses are required to mediate protection. Another challenge will be to produce anti-hookworm vaccine antigens at high yield low cost suitable for immunising large impoverished populations living in the developing nations of the tropics. 相似文献
66.
The binding of Hoechst 33258 and DAPI to five different (A/T)4 sequences in a stable DNA hairpin was studied exploiting the substantial increase in dye fluorescence upon binding. The two dyes have comparable affinities for the AATT site (e.g. association constant K(a)=5.5 x 10(8) M(-1) for DAPI), and their affinities decrease in the series AATT > TAAT approximately equal to ATAT > TATA approximately equal to TTAA. The extreme values of K(a) differ by a factor of 200 for Hoechst 33258 but only 30 for DAPI. The binding kinetics of Hoechst 33258 were measured by stopped-flow under pseudo-first order conditions with an (A/T)4 site in excess. The lower-resolution experiments can be well represented by single exponential processes, corresponding to a single-step binding mechanism. The calculated association-rate parameters for the five (A/T)4 sites are similar (2.46 x 10(8) M(-1) s(-1) to 0.86 x 10(8) M(-1) s(-1)) and nearly diffusion-controlled, while the dissociation-rate parameters vary from 0.42 s(-1) to 96 s(-1). Thus the association constants are kinetically controlled and are close to their equilibrium-determined values. However, when obtained with increased signal-to-noise ratio, the kinetic traces for Hoechst 33258 binding at the AATT site reveal two components. The concentration dependencies of the two time constants and amplitudes are consistent with two different kinetically equivalent two-step models. In the first model, fast bimolecular binding is followed by an isomerization of the initial complex. In the second model, two single-step associations form two complexes that mutually exclude each other. For both models the four reaction-rate parameters are calculated. Finally, specific dissociation kinetics, using poly[d(A-5BrU)], show that the kinetics are even more complex than either two-step model. We correlate our results with the different binding orientations and locations of Hoechst 33258 in the DNA minor groove found in several structural studies in the literature. 相似文献
67.
Hotez PJ Ashcom J Bin Z Bethony J Williamson A Hawdon JM Jianjun F Dobardzic A Rizo I Bolden J Jin Q Yan W Dobardzic R Chung-Debose S Crowell M Datu B Delaney A Dragonovski D Jiang Y Yueyuan L Ghosh K Loukas A Brandt W Russell PK Zook BC 《The Journal of parasitology》2002,88(4):684-690
Laboratory dogs were vaccinated subcutaneously with 3 different recombinant fusion proteins, each precipitated with alum or calcium phosphate. The vaccinated dogs were then challenged orally with 400 third-stage infective larvae (L3) of the canine hookworm, Ancylostoma caninum. The 3 A. caninum antigens selected were Ac-TMP, an adult-specific secreted tissue inhibitor of metalloproteases; Ac-AP, an adult-specific secreted factor Xa serine protease inhibitor anticoagulant; and Ac-ARR-1, a cathepsin D-like aspartic protease. Each of the 3 groups comprised 6 male beagles (8 +/- 1 wk of age). A fourth group comprised control dogs injected with alum. All of the dogs vaccinated with Ac-TMP or Ac-APR-1 exhibited a vigorous antigen-specific antibody response, whereas only a single dog vaccinated with Ac-AP developed an antibody response. Dogs with circulating antibody responses exhibited 4.5-18% reduction in the numbers of adult hookworms recovered from the small intestines at necropsy, relative to alum-injected dogs. In contrast, there was a concomitant increase in the number of adult hookworms recovered from the colon. The increase in colonic hookworms was as high as 500%, relative to alum-injected dogs. Female adult hookworms were more likely to migrate into the colon than were males. Anti-enzyme and anti-enzyme inhibitor antibodies correlated with an alteration in adult hookworm habitat selection in the canine gastroinntestinal tract. 相似文献
68.
69.
The fruit fly, Drosophila melanogaster, has become a popular tool for studying immediate reactions to environmental hazards, such as the heat shock and innate immune responses. In mammals, protective responses to infections and other insults are coordinated by a complex network of cytokines that mediate cell-to-cell signaling. By contrast, the corresponding heat shock and innate immune responses in Drosophila have usually been regarded as cell-autonomous processes. However, in this issue of Developmental Cell, show that cytokines do play a role in mediating an acute phase response in this organism. 相似文献
70.
ARC1 is an E3 ubiquitin ligase and promotes the ubiquitination of proteins during the rejection of self-incompatible Brassica pollen 总被引:24,自引:0,他引:24
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ARC1 is a novel U-box protein required in the Brassica pistil for the rejection of self-incompatible pollen; it functions downstream of the S receptor kinase (SRK). Here, we show that ARC1 has E3 ubiquitin ligase activity and contains several motifs that influence its subcellular localization. ARC1 can shuttle between the nucleus, cytosol, and proteasome/COP9 signalosome (CSN) when expressed in tobacco BY-2 suspension-cultured cells. However, ARC1 localization to the proteasome/CSN occurs only in the presence of an active SRK. In the pistil, ubiquitinated protein levels increase specifically with incompatible pollinations, but they do not change in ARC1 antisense-suppressed pistils. In addition, inhibition of the proteasomal proteolytic activity disrupts the self-incompatibility response. We propose that ARC1 promotes the ubiquitination and proteasomal degradation of compatibility factors in the pistil, which in turn leads to pollen rejection. 相似文献