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  • 1
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: Bacillus subtilis synthesizes polyamines by decarboxylating arginine to agmatine, which is subsequently hydrolysed to putrescine. Spermidine is synthesized from putrescine and decarboxylated S-adenosylmethionine (dAdoMet). In Gram-negative bacteria and in eukaryotes, AdoMet is decarboxylated by an unusual ‘pyruvoyl’ AdoMet decarboxylase (SpeD), the catalytic pyruvoyl moiety of which is generated by serinolysis of an internal serine with self-cleavage of the protein at the upstream peptide bond. Neither the Gram-positive bacterial nor the archaeal counterpart of the Escherichia coli SpeD enzyme were known. We have identified the corresponding B. subtilis speD gene (formely ytcF). Heterologous expression of the cognate Methanococcus jannaschii protein, MJ0315, demonstrated that it displays the same activity as B. subtilis SpeD, indicating that spermidine biosynthesis in Gram-positive bacteria and in archaea follows a pathway very similar to that of Gram-negatives and eukarya. In B. subtilis, transcription of speD is modulated by spermidine and methionine. Its expression is high under usual growth conditions. In contrast, the SpeD protein self-cleaves slowly in vitro, a noticeable difference with its archaeal counterpart. Under certain growth conditions (minimal medium containing succinate and glutamate as a carbon source), speD is co-transcribed with gapB, the gene encoding glyceraldehyde-3-phosphate dehydrogenase, an enzyme required for gluconeogenesis. This observation may couple polyamine metabolism to sulphur and carbon metabolism by a so far unknown mechanism.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: PrfA is the major regulator of Listeria virulence gene expression. This protein is a member of the Crp/Fnr family of transcription regulators. To gain a deeper understanding of the PrfA regulon, we constructed a whole-genome array based on the complete genome sequence of Listeria monocytogenes strain EGDe and evaluated the expression profiles of the wild-type EGDe and a prfA-deleted mutant (EGDe ΔprfA). Both strains were grown at 37°C in brain–heart infusion broth (BHI) and BHI supplemented with either activated charcoal, a compound known to enhance virulence gene expression, or cellobiose, a sugar reported to downregulate virulence gene expression in spite of full expression of PrfA. We identified three groups of genes that are regulated differently. Group I comprises, in addition to the 10 already known genes, two new genes, lmo2219 and lmo0788, both positively regulated and preceded by a putative PrfA box. Group II comprises eight negatively regulated genes: lmo0278 is preceded by a putative PrfA box, and the remaining seven genes (lmo0178–lmo0184) are organized in an operon. Group III comprises 53 genes, of which only two (lmo0596 and lmo2067) are preceded by a putative PrfA box. Charcoal addition induced upregulation of group I genes but abolished regulation by PrfA of most group III genes. In the presence of cellobiose, all the group I genes were downregulated, whereas group III genes remained fully activated. Group II genes were repressed in all conditions tested. A comparison of the expression profiles between a second L. monocytogenes strain (P14), its spontaneous mutant expressing a constitutively active PrfA variant (P14prfA*) and its corresponding prfA-deleted mutant (P14ΔprfA) and the EGDe strain revealed interesting strain-specific differences. Sequences strongly similar to a sigma B-dependent promoter were identified upstream of 22 group III genes. These results suggest that PrfA positively regulates a core set of 12 genes preceded by a PrfA box and probably expressed from a sigma A-dependent promoter. In contrast, a second set of PrfA-regulated genes lack a PrfA box and are expressed from a sigma B-dependent promoter. This study reveals that PrfA can act as an activator or a repressor and suggests that PrfA may directly or indirectly activate different sets of genes in association with different sigma factors.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 0749-503X
    Schlagwort(e): chromosome III ; drug-sensitivity/resistance ; functional analysis ; genome ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: In 1993, a pilot project for the functional analysis of newly discovered open reading frames, presumably coding for proteins, from yeast chromosome III was launched by the European Community. In the frame of this programme, we have developed a large-scale screening for the identification of gene/protein functions via systematic phenotypic analysis. To this end, some 80 haploid mutant yeast strains were constructed, each carrying a targeted deletion of a single gene obtained by HIS3 or TRP1 transplacement in the W303 background and a panel of some 100 growth conditions was established, ranging from growth substrates, stress to, predominantly, specific inhibitors and drugs acting on various cellular processes. Furthermore, co-segregation of the targeted deletion and the observed phenotype(s) in meiotic products has been verified. The experimental procedure, using microtiter plates for phenotypic analysis of yeast mutants, can be applied on a large scale, either on solid or in liquid media. Since the minimal working unit of one 96-well microtiter plate allows the simultaneous analysis of at least 60 mutant strains, hundreds of strains can be handled in parallel. The high number of monotropic and pleiotropic phenotypes (62%) obtained, together with the acquired practical experience, have shown this approach to be simple, inexpensive and reproducible. It provides a useful tool for the yeast community for the systematic search of biochemical and physiological functions of unknown genes accounting for about a half of the 6000 genes of the complete yeast genome. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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