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81.
The phylogenetic origin of the bifunctional tyrosine-pathway protein in the enteric lineage of bacteria 总被引:5,自引:0,他引:5
Because bifunctional enzymes are distinctive and highly conserved products
of relatively infrequent gene-fusion events, they are particularly useful
markers to identify clusters of organisms at different hierarchical levels
of a phylogenetic tree. Within the subdivision of gram-negative bacteria
known as superfamily B, there are two distinctive types of tyrosine-pathway
dehydrogenases: (1) a broad- specificity dehydrogenase (recently termed
cyclohexadienyl dehydrogenase [CDH]) that can utilize either prephenate or
L-arogenate as alternative substrates and (2) a bifunctional CDH that also
posseses chorismate mutase activity. (T-proteins). The bifunctional
T-protein, thought to be encoded by fused ancestral genes for chorismate
mutase and CDH, was found to be present in enteric bacteria (Escherichia,
Shigella, Salmonella, Citrobacter, Klebsiella, Erwinia, Serratia,
Morganella, Cedecea, Kluyvera, Hafnia, Edwardsiella, Yersinia, and Proteus)
and in Aeromonas and Alteromonas. Outside of the latter "enteric lineage,"
the T-protein is absent in other major superfamily-B genera, such as
Pseudomonas (rRNA homology group I), Xanthomonas, Acinetobacter, and
Oceanospirillum. Hence, the T-protein must have evolved after the
divergence of the enteric and Oceanospirillum lineages.
3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase-phe, an early-pathway
isozyme sensitive to feedback inhibition by L- phenylalanine, has been
found in each member of the enteric lineage examined. The absence of both
the T-protein and DAHP synthase-phe elsewhere in superfamily B indicates
the emergence of these character states at approximately the same
evolutionary time.
相似文献
82.
Biotinyl-oligosaccharides are a relatively new generation of saccharide
probes that enable immobilization of desired oligosaccharides on
streptavidin matrices for studies of carbohydrate-protein interactions.
Here we describe the facile preparation of biotinyl-l-3-(2-naphthyl)-
alanine hydrazide (BNAH) derivatives of oligosaccharides, containing a
strong UV absorbing and fluorescent group, in which the ring of the
reducing-end monosaccharide is nonreduced. We evaluate reactivities of
immobilized BNAH- N -glycans with plant lectins that recognize aspects of
the oligosaccharide core or outer-arms. We make some comparisons with
2-amino-6-amidobiotinyl-pyridine (BAP) derivatives obtained by reductive
amination, and 6-(biotinyl)-aminocaproyl-hydrazide (BACH) derivatives which
have a longer spacer-arm. N -Glycan-BNAH and-BAP derivatives have, overall,
comparable reactivities with lectins which recognize N -glycan outer-arms
or the trimannosyl core, but only BNAH and BACH derivatives are bound by
lectins which recognize the non- reduced core. Moreover, with Pisum sativum
agglutinin (PSA) which additionally requires the fucosyl- N-
glycan-asparaginyl core for high affinity binding, the immobilized BNAH
derivative (which is an alanine hydrazide beta-glycoside) can substitute
for the natural beta- glycosylasparaginyl core, whereas the BACH derivative
(aminocaproyl- hydrazide-beta-glycoside) is less effective. BNAH is a
derivatization reagent of choice, therefore, for solid phase
carbohydrate-binding experiments with immobilized N -glycans.
相似文献
83.
Multidimensional heteronuclear NMR studies have been applied to the
resonance assignment and conformational analysis of 13C-enriched
Neu5Acalpha2-3Galbeta1-4Glc. It is demonstrated that three-dimensional
ROESY-HSQC experiments provide through-space distance restraints which
cannot be observed with conventional homonuclear 1H techniques due to
resonance overlap. In particular, connectivities demonstrating the
existence of the "anti" conformation about the Galbeta1-4Glc glycosidic
linkage are unambiguously observed. It is shown that 13C isotopic
enrichment of the trisaccharide at a level >95% enables straightforward
measurement of trans-glycosidic 1H-13C and 13C-13C coupling constants and a
Karplus-type relation is derived for the latter. In total 15 conformational
restraints were obtained for the trisaccharide in aqueous solution, all of
which were in excellent agreement with theoretical parameters computed from
a 5 ns molecular dynamics simulation of the glycan.
相似文献
84.
Molecular phylogenetics of Stenodermatini bat genera: congruence of data from nuclear and mitochondrial DNA 总被引:2,自引:1,他引:1
Van den Bussche RA; Baker RJ; Wichman HA; Hamilton MJ 《Molecular biology and evolution》1993,10(5):944-959
Within the tribe Stenodermatini the systematics of the complex of species
allied with the genus Artibeus has generated several alternative
phylogenetic hypotheses. The most recent treatment recognized four genera
(Artibeus, Dermanura, Enchisthenes, and Koopmania) and suggested that the
most recent common ancestor of these four genera would include the common
ancestor of all other currently recognized Stenodermatini genera except
Sturnira. To test this hypothesis, we examined an EcoRI-defined nuclear
satellite DNA repeat and 402 bp of DNA sequence variation from the
mitochondrial cytochrome b gene. Phylogenetic conclusions based on Southern
blot analyses, in situ hybridization, and mitochondrial DNA sequence data
indicate that Enchisthenes is not closely related to Dermanura, Artibeus,
or Koopmania and that Dermanura, Artibeus, and Koopmania shared a common
ancestor after diverging from the remainder of the Stenodermatini. If our
conclusions are correct, then justification for recognizing Dermanura and
Koopmania as generically distinct from Artibeus must be based on the
magnitude of difference that distinguishes each rather than on the
conclusion that to place them as congeneric with Artibeus creates a
paraphyletic taxon.
相似文献
85.
86.
Fourteen native strains of Trichoderma spp. from wildand agricultural pathosystems in the state of Yucatan, Mexico, with growth-promoting ability of Capsicum chinense Jacq. seedlings were evaluated and antagonistic effect of their filtrate against second-stage juveniles (J2) of Meloidogyne incognita. The strains Th05-02 and Th27-08 showed the best significant effects on plant hight variable increments 55.57 and 47.62%, theTh07-04 with 29.48% more root length, theTh02-01 and Th07-04 isolates increased from 48.71 to 84.61% in volume radical and 53.40% of total dry biomass. Statistical analysis (p≤0.001) of Th43 and Th43-13-14 filtrates caused 100% mortality at 24 and 48h. In the test of reversibility to 24 h after replacing the filtrates Th43-13, Th43-14, TH09-06 and TH20-07 by sterile distilled water, the J2 did not recover their viability, so they were considered as the best potential strains of Trichoderma spp. with antagonistic capacity in J2 of M.incognita. 相似文献
87.
Soares Medeiros LC Gomes F Maciel LR Seabra SH Docampo R Moreno S Plattner H Hentschel J Kawazoe U Barrabin H de Souza W Damatta RA Miranda K 《The Journal of eukaryotic microbiology》2011,58(5):416-423
The structural organization of parasites has been the subject of investigation by many groups and has lead to the identification of structures and metabolic pathways that may represent targets for anti-parasitic drugs. A specific group of organelles named acidocalcisomes has been identified in a number of organisms, including the apicomplexan parasites such as Toxoplasma and Plasmodium, where they have been shown to be involved in cation homeostasis, polyphosphate metabolism, and osmoregulation. Their structural counterparts in the apicomplexan parasite Eimeria have not been fully characterized. In this work, the ultrastructural and chemical properties of acidocalcisomes in Eimeria were characterized. Electron microscopy analysis of Eimeria parasites showed the dense organelles called volutin granules similar to acidocalcisomes. Immunolocalization of the vacuolar proton pyrophosphatase, considered as a marker for acidocalcisomes, showed labeling in vesicles of size and distribution similar to the dense organelles seen by electron microscopy. Spectrophotometric measurements of the kinetics of proton uptake showed a vacuolar proton pyrophosphatase activity. X-ray mapping revealed significant amounts of Na, Mg, P, K, Ca, and Zn in their matrix. The results suggest that volutin granules of Eimeria parasites are acidic, dense organelles, and possess structural and chemical properties analogous to those of other acidocalcisomes, suggesting a similar functional role in these parasites. 相似文献
88.
目的:建立丙型肝炎病毒NS3/4A丝氨酸蛋白酶体内活性评价模型。方法:利用NS4A/B是NS3/4A丝氨酸蛋白酶作用底物的特性,构建融合基因NS3/NS4A/B-SEAP,底物片段NS4A/B插在NS3/4A和人分泌性碱性磷酸酶(SEAP)之间,融合基因表达后SEAP的分泌依赖于有活性的NS3/4A在NS4A/B位点的切割。将含融合基因的质粒NS3/4A(△4AB)SEAP通过水动力转染技术转染到小鼠体内,检测小鼠血清中SEAP的活性,高活性的SEAP是该评价体系成立的证据。结果与结论:在瞬时表达NS3/4A的小鼠血清中检测到了高活性的SEAP,建立了可用于评价抗NS3/4A的小鼠体内瞬时模型。 相似文献
89.
Santos TA Portes Jde A Damasceno-Sá JC Caldas LA Souza Wd Damatta RA Seabra SH 《PloS one》2011,6(11):e27867
Phosphatidylserine (PS) exposure on the cell surface indicates apoptosis, but has also been related to evasion mechanisms of parasites, a concept known as apoptotic mimicry. Toxoplasma gondii mimics apoptotic cells by exposing PS, inducing secretion of TGF-beta1 by infected activated macrophages leading to degradation of inducible nitric oxide (NO) synthase, NO production inhibition and consequently persisting in these cells. Here PS+ and PS− subpopulation of tachyzoites were separated and the entrance mechanism, growth and NO inhibition in murine macrophages, and mice survival and pathology were analyzed. Infection index in resident macrophages was similar for both PS subpopulations but lower when compared to the total T. gondii population. Growth in resident macrophages was higher for the total T. gondii population, intermediate for the PS+ and lower for the PS− subpopulation. Production of NO by activated macrophages was inhibited after infection with the PS+ subpopulation and the total populations of tachyzoites. However, the PS− subpopulation was not able to inhibit NO production. PS+ subpopulation invaded macrophages by active penetration as indicated by tight-fitting vacuoles, but the PS− subpopulation entered macrophages by phagocytosis as suggested by loose-fitting vacuoles containing these tachyzoites. The entrance mechanism of both subpopulations was confirmed in a non-professional phagocytic cell line where only the PS+ tachyzoites were found inside these cells in tight-fitting vacuoles. Both subpopulations of T. gondii killed mice faster than the total population. Clear signs of inflammation and no tachyzoites were seen in the peritoneal cavity of mice infected with the PS− subpopulation. Moreover, mice infected with the PS+ subpopulation had no sign of inflammation and the parasite burden was intense. These results show that PS+ and PS− subpopulations of T. gondii are necessary for a successful toxoplasma infection indicating that both subpopulations are required to maintain the balance between inflammation and parasite growth. 相似文献
90.
JOSÉ MIGUEL APARICIO ALBERTO MUÑOZ RAÚL BONAL ANDERS PAPE MØLLER 《Biological journal of the Linnean Society. Linnean Society of London》2012,105(4):925-936
Many organisms show well‐defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost tail feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of tail feathers in relation to body size and wing size. Tail feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer tails. The extra enlargement of the tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying feather structure to produce longer feathers of lower density. These two separate processes accounting for the production of longer and more costly tail feathers and less dense feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 925–936. 相似文献