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1.
Ze'ev Barak Bela Ohana Yael Allon Joel Margalit 《Applied microbiology and biotechnology》1987,27(1):88-93
Summary PST, a spontaneous mutant of Bacillus thuringiensis var. israelensis (B.t.i.) resistant to penicillin, streptomycin and tetracycline was isolated by serial selections. In the absence of antibiotics it showed genetic stability for 16 generations. Mosquito larvicidal activity of PST was similar to that of B.t.i., its parental strain. It also maintained the specific antigenicity of B.t.i. although its rate of growth was somewhat lower, a generation time of 55 min for PST vs. 38 min for B.t.i. Cell concentration plays a major role in the phenomenon of PST resistance to penicillin.This antibiotic resistant mutant of b.t.i. provides us with an efficient tool to trace B.t.i. among the indigenous bacteria present in septic habitats in the field as well as inside the larval gut. 相似文献
2.
Distribution of δ-aminolevulinic acid biosynthetic pathways among phototrophic bacterial groups 总被引:12,自引:0,他引:12
Two biosynthetic pathways are known for the universal tetrapyrrole precursor, -aminolevulinic acid (ALA). In the ALA synthase pathway which was first described in animal and some bacterial cells, the pyridoxal phosphate-dependent enzyme ALA synthase catalyzes condensation of glycine and succinyl-CoA to form ALA with the loss of C-1 of glycine as CO2. In the five-carbon pathway which was first described in plant and algal cells, the carbon skeleton of glutamate is converted intact to ALA in a proposed reaction sequence that requires three enzymes, tRNAGlu, ATP, Mg2+, NADPH, and pyridoxal phosphate. We have examined the distribution of the two ALA biosynthetic pathways among various genera, using cell-free extracts obtained from representative organisms. Evidence for the operation of the five-carbon pathway was obtained by the measurement of RNase-sensitive label incorporation from glutamate into ALA, using 3,4-[3H]glutamate or 1-[14C]glutamate as substrate. ALA synthase activity was indicated by RNase-insensitive incorporation of label from 2-[14C]glycine into ALA. The distribution of the two pathways among the bacteria tested was in general agreement with their previously established phylogenetic relationships and clearly indicates that the five-carbon pathway is the more ancient process, whereas the pathway utilizing ALA synthase probably evolved much later. The five-carbon pathway is apparently the more widely utilized one among bacteria, while the ALA synthase pathway seems to be limited to the subgroup of purple bacteria.Abbreviations ALA
-aminolevulinic acid
- DTT
dithiothreitol
- PALP
pyridoxal phosphate
- SDS
sodium dodecyl sulfate
- tricine
N-tris-(hydroxymethyl)methylglycine 相似文献
3.
Jacob Gopas Dganit Itzhaky Yael Segev Samuel Salzberg Barry Trink Noah Isakov Bracha Rager-Zisman 《Cancer immunology, immunotherapy : CII》1992,34(5):313-320
The effect of persistent measles virus infection on the expression of major histocompatibility complex (MHC) class I antigens was studied. Mouse neuroblastoma cells C1300, clone NS20Y, were persistently infected with the Edmonston strain of measles virus. The persistently infected cell line, NS20Y/MS, expressed augmented levels of both H-2Kk and H-2Dd MHC class I glycoproteins. Activation of two interferon(IFN)-induced enzymes, known to be part of the IFN system: (2–5)oligoadenylate synthetase and double-stranded-RNA-activated protein kinase, was detected. Measles-virus-infected cells elicited cytotoxic T lymphocytes that recognized and lysed virus-infected and uninfected neuroblastoma cells in an H-2-restricted fashion. Furthermore, immunization of mice with persistently infected cells conferred resistance to tumor growth after challenge with the highly malignant NS20Y cells. The rationale for using measles virus for immunotherapy is that most patients develop lifelong immunity after recovery or vaccination from this infection. Patients developing cancer are likely to have memory cells. A secondary response induced by measles-virus-infected cells may therefore induce an efficient immune response against non-infected tumour cells. 相似文献
4.
Debabrata Majumdar Yael J. Avissar James H. Wyche Samule I. Beale 《Archives of microbiology》1991,156(4):281-289
The green sulfur bacterium, Chlorobium vibrioforme, synthesizes the tetrapyrrole precursor, -aminolevulinic acid (ALA), from glutamate via the RNA-dependent five-carbon pathway. A 1.9-kb clone of genomic DNA from C. vibrioforme that is capable of transforming a glutamyl-tRNA reductase-deficient, ALA-dependent, hemA mutant of Escherichia coli to prototrophy was sequenced. The transforming C. vibrioforme DNA has significant sequence similarity to the E. coli, Salmonella typhimurium, and Bacillus subtilis hemA genes and contains a 1245 base open reading frame that encodes a 415 amino acid polypeptide with a calculated molecular weight of 46174. This polypeptide has over 28% amino acid identity with the polypeptides deduced from the nucleic acid sequences of the E. coli, S. typhimurium, and B. subtilis hemA genes. No sequence similarity was detected, at either the nucleic acid or the peptide level, with the Rhodobacter capsulatus or Bradyrhizobium japonicum hemA genes, which encode ALA synthase, or with the S. typhimurium hemL gene, which encodes glutamate-1-semialdehyde aminotransferase. These results establish that hemA encodes glutamyl-tRNA reductase in species that use the five-carbon ALA biosynthetic pathway. A second region of the cloned DNA, located downstream from the hemA gene, has significant sequence similarity to the E. coli and B. subtilis hemC genes. This region contains a potential open reading frame that encodes a polypeptide that has high sequence identity to the deduced E. coli and B. subtilis HemC peptides. hemC encodes the tetrapyrrole biosynthetic enzyme, porphobilinogen deaminase, in these species. Preliminary evidence was obtained for the existence of a 3.0-kb polycistronic meassge that includes the hemA sequence, in exponentially growing C. vibrioforme cells. Results of condon usage analysis for the C. vibrioforme hemA gene indicate that green sulfur bacteria are more closely related to purple nonsulfur bacteria than to enteric bacteria. Sequences corresponding to a polyadenylation signal and a poly(A) attachment site were found immediately downstream from the 3 end of the hemA open reading frame. 相似文献
5.
When larvae of Tribolium castaneum were reared on diets deficient in thiamine, pyridoxine or riboflavin mortality was high and the rate of development was slow. The few surviving larvae did attain the same final stage as larvae developing on an all-vitamin control. On diets deficient in nicotinic acid, calcium pantothenate or choline chloride all aspects of development were impaired and no pupation occurred. The negative effects of folic acid deficiency were more pronounced in the pupal stage than in the larval instars. The dietary deficiency of folic acid, choline chloride or thiamine, had no apparent effect on adult fecundity, and a dietary deficiency of any one of the seven vitamins assayed did not adversely affect egg fertility.
Résumé Une mortalité importante a été constatée chez des larves de Tribolium castaneum élevées sur des régimes déficitaires en thiamine, pyridoxine et riboflavine. Le développement a été ralenti d'une façon considérable, mais les larves qui ont survécu sont arrivées au même stade final que les larves témoins nourries avec toutes les vitamines. Tous les autres régimes alimentaires ont été moins adéquates que celui contenant un supplément de levure. L'effet de l'absence de l'acide nicotinique, du pantothenate de calcium ou bien du chlorure de choline a été encore plus net, car les larves ne se sont pas nymphosées. Cet effet prononcé de l'insuffisance du chlorure de choline contraste avec la réaction de Tribolium confusum à l'absence de chlorure de choline dans le régime alimentaire.Le développement larvaire a été peu affecté par l'absence de l'acide folique. Mais, durant la nymphose, les effets négatifs se manifestent davantage encore. L'absence de pyridoxine, riboflavine, acide nicotinique ou pantothenate du calcium a réduit d'une façon importante le taux initial de la fécondité des adultes de T. castaneum. L'absence de l'acide folique, chlorure de choline ou thiamine n'a pas été marquée par un effet semblable. La fertilité des ufs n'a pas été affectée par le manque d'une vitamine quelconque.Ces résultats indiquent que le chlorure de choline et la thiamine sont nécessaires pour le développement larvaire, mais qu'elles sont peu importantes pour la vitalité des adultes. Les réserves en certaines vitamines essentielles chez les nymphes suffisent donc aux exigences des adultes, au moins pendant quelques mois après leur éclosion.相似文献
6.
7.
Characterization of Nine Novel Mutations in the CD40 Ligand Gene in Patients with X-Linked Hyper IgM Syndrome of Various Ancestry 总被引:3,自引:0,他引:3
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Paolo Macchi Anna Villa Dario Strina Maria Grazia Sacco Federica Morali Duilio Brugnoni Silvia Giliani Elide Mantuano Anders Fasth Bengt Andersson Ben J. M. Zegers Giovanni Cavagni Igor Reznick Jacov Levy Israel Zan-Bar Yael Porat Paolo Air Alessandro Plebani Paolo Vezzoni Luigi D. Notarangelo 《American journal of human genetics》1995,56(4):898-906
X-linked immunodeficiency with hyper-IgM (HIGMX-1) is a rare disorder caused by defective expression of the CD40 ligand (CD40L) by activated T lymphocytes, resulting in inefficient T-B cell cooperation and failure of B cells to undergo immunoglobulin isotype switch. In the present work, we describe nine patients of various ancestry who bear different mutations in the X chromosome–specific CD40L gene. Two of the mutations were nonsense mutations, one each resulting in premature stop codons at amino acid residues 39 and 140. Three patients had single point missense mutations, one each at codons 126, 140, and 144. Another patient had a 4-bp genomic deletion in exon 2, resulting in a frameshift and premature termination. Three patients showed insertions, one each of 1, 2, and 4 nt, probably because of polymerase slippage, resulting in frameshift mutation and premature termination. Overall, these observations confirm the heterogeneity of mutations in HIGMX-1. However, the identification of two patients whose mutation involves codon 140 (previously shown to be altered in two other unrelated subjects) suggests that this may be a hotspot of mutation in HIGMX-1. In two additional patients with clinical and immunological features indistinguishable from canonical HIGMX-1, no mutation was detected in the coding sequence, in the 5' flanking region, or in the 3' UTR. 相似文献
8.
Summary The inner enamel epithelium (IEE) covers the labial tooth aspect as a one cell layer which, when cut sagittally, appears as a longitudinal cell column extending from the tooth origin toward the periphery. Following sudden tooth shortening, the IEE responds by an increased cell production which later declines below normal values. The perturbation affects all cell kinetic parameters; the progenitor compartment, which initially increases, diminishes in size toward end of the experiment. The cell cycle transition times, which initially decline, rise toward the end of the experiment. The mean normal daily cell production rate of 70 cell % (i.e. 70 cells are produced by 100 progenitors) increases to 111 cell % and then declines to a low of 51 cell %. The IEE response typifies the behavior of other cell renewal systems such as intestinal epithelium and epidermis. 相似文献
9.
The complex pathway of tetrapyrrole biosynthesis can be dissected into five sections: the pathways that produce 5-aminolevulinate (the C-4 and the C-5 pathways), the steps that transform ALA to uroporphyrinogen III, which are ubiquitous in the biosynthesis of all tetrapyrroles, and the three branches producing specialized end products. These end products include corrins and siroheme, chlorophylls and hemes and linear tetrapyrroles. These branches have been subjects of recent reviews. This review concentrates on the early steps leading up to uroporphyrinogen III formation which have been investigated intensively in recent years in animals, in plants, and in a wide range of bacteria.Abbreviations ALA
5-aminolevulinic acid
- ALAS
5-aminolevulinic acid synthase
- GR
glutamyl-tRNA reductase
- GSA
glutamate-1-semialdehyde
- GSAT
glutamate-1-semialdehyde aminotransferase
- HMB
hydroxymethylbilane
- PBG
porphobilinogen
- PBGD
porphobilinogen deaminase
- PBGS
porphobilinogen synthase
- URO
uroporphyrin
- URO'gen
uroporphyrinogen
- US
uroporphyrinogen III synthase 相似文献
10.
Alternative splicing constitutes a major mechanism creating protein diversity in humans. This diversity can result from the alternative skipping of entire exons or by alternative selection of the 5′ or 3′ splice sites that define the exon boundaries. In this study, we analyze the sequence and evolutionary characteristics of alternative 3′ splice sites conserved between human and mouse genomes for distances ranging from 3 to 100 nucleotides. We show that alternative splicing events can be distinguished from constitutive splicing by a combination of properties which vary depending on the distance between the splice sites. Among the unique features of alternative 3′ splice sites, we observed an unexpectedly high occurrence of events in which a polypyrimidine tract was found to overlap the upstream splice site. By applying a machine-learning approach, we show that we can successfully discriminate true alternative 3′ splice sites from constitutive 3′ splice sites. Finally, we propose that the unique features of the intron flanking alternative splice sites are indicative of a regulatory mechanism that is involved in splice site selection. We postulate that the process of splice site selection is influenced by the distance between the competitive splice sites. 相似文献