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Clinkenbeard Erica L. Turpin Courtney Jiang Jieyun Peterson Martha L. Spear Brett T. 《Mammalian genome》2019,30(7-8):226-236
Mammalian Genome - BALB/cJ mice exhibit considerable phenotypic differences with other BALB/c substrains. Some of these traits involve the liver, including persistent postnatal expression of genes... 相似文献
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Background
The γ-proteobacterium Francisella tularensis is the etiologic agent of seasonal tick-transmitted tularemia epizootics in rodents and rabbits and of incidental infections in humans. The biology of F. tularensis in its tick vectors has not been fully described, particularly with respect to its quanta and duration of colonization, tissue dissemination, and transovarial transmission. A systematic study of the colonization of Dermacentor variabilis by the F. tularensis subsp. holarctica live vaccine strain (LVS) was undertaken to better understand whether D. variabilis may serve as an inter-epizootic reservoir for F. tularensis.Methodology/Principal Findings
Colony-reared larva, nymph, and adult D. variabilis were artificially fed LVS via glass capillary tubes fitted over the tick mouthparts, and the level of colonization determined by microbial culture. Larvae and nymphs were initially colonized with 8.8±0.8×101 and 1.1±0.03×103 CFU/tick, respectively. Post-molting, a significant increase in colonization of both molted nymphs and adults occurred, and LVS persisted in 42% of molted adult ticks at 126 days post-capillary tube feeding. In adult ticks, LVS initially colonized the gut, disseminated to hemolymph and salivary glands by 21 days, and persisted up to 165 days. LVS was detected in the salivary secretions of adult ticks after four days post intra-hemocoelic inoculation, and LVS recovered from salivary gland was infectious to mice with an infectious dose 50% of 3 CFU. LVS in gravid female ticks colonized via the intra-hemocoelic route disseminated to the ovaries and then to the oocytes, but the pathogen was not recovered from the subsequently-hatched larvae.Conclusions/Significance
This study demonstrates that D. variabilis can be efficiently colonized with F. tularensis using artificial methods. The persistence of F. tularensis in D. variabilis suggests that this tick species may be involved in the maintenance of enzootic foci of tularemia in the central United States. 相似文献4.
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Characterization of human HtrA2, a novel serine protease involved in the mammalian cellular stress response. 总被引:21,自引:0,他引:21
C W Gray R V Ward E Karran S Turconi A Rowles D Viglienghi C Southan A Barton K G Fantom A West J Savopoulos N J Hassan H Clinkenbeard C Hanning B Amegadzie J B Davis C Dingwall G P Livi C L Creasy 《European journal of biochemistry》2000,267(18):5699-5710
Human HtrA2 is a novel member of the HtrA serine protease family and shows extensive homology to the Escherichia coli HtrA genes that are essential for bacterial survival at high temperatures. HumHtrA2 is also homologous to human HtrA1, also known as L56/HtrA, which is differentially expressed in human osteoarthritic cartilage and after SV40 transformation of human fibroblasts. HumHtrA2 is upregulated in mammalian cells in response to stress induced by both heat shock and tunicamycin treatment. Biochemical characterization of humHtrA2 shows it to be predominantly a nuclear protease which undergoes autoproteolysis. This proteolysis is abolished when the predicted active site serine residue is altered to alanine by site-directed mutagenesis. In human cell lines, it is present as two polypeptides of 38 and 40 kDa. HumHtrA2 cleaves beta-casein with an inhibitor profile similar to that previously described for E. coli HtrA, in addition to an increase in beta-casein turnover when the assay temperature is raised from 37 to 45 degrees C. The biochemical and sequence similarities between humHtrA2 and its bacterial homologues, in conjunction with its nuclear location and upregulation in response to tunicamycin and heat shock suggest that it is involved in mammalian stress response pathways. 相似文献
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H M Miziorko K D Clinkenbeard W D Reed M D Lane 《The Journal of biological chemistry》1975,250(15):5768-5773
Homogeneous liver 3-hydroxy-3-methylglutaryl coenzyme A synthase, which catalyzes the condensation of acetyl-CoA with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA, also carries out: (a) a rapid transacetylation from acetyl-CoA to 31-dephospho-CoA and (b) a slow hydrolysis of acetyl-CoA to acetate and CoA. Transacetylation and hydrolysis occur at 50 and 1 percent, respectively, the rate of the synthasecatalyzed condensation reaction. It appears that an acetyl-enzyme intermediate is involved in the transacetylase and hydrolase reactions of 3-hydroxy-3-methylglutaryl-CoA synthase, as well as in the over-all condensation process. Covalent binding to the enzyme of a [14C]acetyl group contributed by [1(-14)C]acetyl-CoA is indicated by migration of the [14C]acetyl group with the dissociated synthase upon electrophoresis in dodecyl sulfate-urea and by precipitation of [14C]acetyl-enzyme with trichloroacetic acid. At 0 degrees and a saturating level of acetyl-CoA, the synthase is rapidly (less than 20 s) acetylated yielding 0.6 acetyl group/enzyme dimer. Performic acid oxidation completely deacetylates the enzyme, suggesting the site of acetylation to be a cysteinyl sulfhydryl group. Proteolytic digestion of [14C]acetyl-S-enzyme under conditions favorable for intramolecular S to N acetyl group transfer quantitatively liberates a labeled derivative with a [14C]acetyl group stable to performic acid oxidation. The labeled oxidation product is identified as N-[14C]acetylcysteic acid, thus demonstrating a cysteinyl sulfhydryl group as the original site of acetylation. The ability of the acetylated enzyme, upon addition of acetoacetyl-CoA, to form 3-hydroxy-3-methylglutaryl-CoA indicates that the acetylated cysteine residue is at the catalytic site. 相似文献
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Mitochondrial DNAs of six morphologically different Phytophthora species were digested with 15 restriction enzymes. The numbers of restriction fragments obtained differed considerably from those theoretically expected for random base distribution. Enzymes with relatively many G and C in their recognition sequences produced significantly larger numbers of fragments. Moreover, fragments generated by most of these enzymes were more often shared by two or more species than those from enzymes with more A and T in their recognition sequence. It is concluded that base distribution in mitochondrial DNA of Phytophthora is heterogeneous,AT-rich stretches occurring scattered over the mitochondrial genome and GC-rich regions present in conserved sequences, presumably genes. A practical consequence for taxonomic RFLP studies is that optimal enzymes can be selected, depending on the desired level of resolution. 相似文献
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The 18S ribosomal RNAs of 21 tetrapods were sequenced and aligned with five
published tetrapod sequences. When the coelacanth was used as an outgroup,
Lissamphibia (living amphibians) and Amniota (amniotes) were found to be
statistically significant monophyletic groups. Although little resolution
was obtained among the lissamphibian taxa, the amniote sequences support a
sister-group relationship between birds and mammals. Portions of the 28S
ribosomal RNA (rRNA) molecule in 11 tetrapods also were sequenced, although
the phylogenetic results were inconclusive. In contrast to previous
studies, deletion or down- weighting of base-paired sites were found to
have little effect on phylogenetic relationships. Molecular evidence for
amniote relationships is reviewed, showing that three genes
(beta-hemoglobin, myoglobin, and 18S rRNA) unambiguously support a
bird-mammal relationship, compared with one gene (histone H2B) that favors
a bird- crocodilian clade. Separate analyses of four other genes (alpha-
crystallin A, alpha-hemoglobin, insulin, and 28S rRNA) and a combined
analysis of all sequence data are inconclusive, in that different groups
are defined in different analyses and none are strongly supported. It is
suggested that until sequences become available from a broader array of
taxa, the molecular evidence is best evaluated at the level of individual
genes, with emphasis placed on those studies with the greatest number of
taxa and sites. When this is done, a bird-mammal relationship is most
strongly supported. When regarded in combination with the morphological
evidence for this association, it must be considered at least as plausible
as a bird-crocodilian relationship.
相似文献
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K D Clinkenbeard W D Reed R A Mooney M D Lane 《The Journal of biological chemistry》1975,250(8):3108-3116
Acetoacetyl-CoA thiolase and 3-hydroxy-3-methylglutaryl coenzyme synthase which comprise the 3-hydroxy-3-methylglutaryl-CoA-generating system(s) for hepatic cholesterogenesis and ketogenesis exhibit dual mitochondrial and cytoplasmic localization. Twenty to forty per cent of the thiolase and synthase of avian and rat liver are localized in the cytoplasmic compartment, the remainder residing in the mitochondria. In contrast, 3-hydroxy-3 methylglutaryl-CoA lyase, an enzyme unique to the "3-hydroxy-3-methylglutaryl-CoA cycle" of ketogenesis, appears to be localized in the mitochondrion. The small proportion, 4 to 8 percent, of this enzyme found in the cytoplasmic fraction appears to arise via leakage from the mitochondria during cell fractionation in that its properties, pI and stability, are identical to those of the mitochondrial lyase. These results are consistent with the view that ketogenesis which involves all three enzymes, acetoacetyl-CoA thiolase, 3-hydroxy-3-methylglutaryl-CoA synthase and 3-hydroxy-3-methylglutaryl-CoA lyase, occurs exclusively in the mitochondrion, whereas cholesterogenesis, a pathway which involves only the 3-hydroxy-3-methylglutaryl-CoA synthesizing enzymes, is restricted to the cytoplasm. Further fractionation of isolated mitochondria from chicken and rat liver showed that all three of the 3-hydroxy-3-methylglutaryl-CoA cycle enzymes are soluble and are localized within the matrix compartment of the mitochondrion. Likewise, cytoplasmic acetoacetyl-CoA thiolase and 3-hydroxy-3-methylglutaryl-CoA synthase are soluble cytosolic enzymes, no thiolase or synthase activity being detectable in the microsomal fraction. Chicken liver mitochondrial 3-hydroxy-3methylglutaryl-CoA synthase activity consists of a single enzymic species with a pI of 7.2, whereas the cytoplasmic activity is composed of at least two species with pI values of 4.8 and 6.7. Thus it is evident that the mitochondrial and cytoplasmic species are molecularly distinct as has been shown to be the case for the mitochondrial and cytoplasmic acetoacetyl-CoA thiolases from avian liver (Clinkenbeard, K. D., Sugiyama, T., Moss, J., Reed, W. D., and Lane, M. D. (1973) J. Biol. Chem. 248, 2275). Substantial mitochondrial 3-hydroxy-3-methylglutaryl-CoA lyase activity is present in all tissues surveyed, while only liver and kidney possess significant mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity. Therefore, it is proposed that tissues other than liver and kidney are unable to generate acetoacetate because they lack the mitochondrial synthase. 相似文献
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