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11.
Heinz Rotering Waltraud Fiedler Wolfgang Rollinger Volkmar Braun 《FEMS microbiology letters》1984,22(1):61-68
Abstract A mutant screening procedure is described which allows the identification of mutants carrying lesions in lipoprotein, membrane-derived oligosac-charides (MDO), and other compounds of the E. coli cell envelope containing glycerol derived from phospholipid metabolism. Two mutants lacking glycerol in MDO and one mutant devoid of lipoprotein demonstrate the usefulness of the procedure. 相似文献
12.
An enzyme was identified in human serum which unlike lysozyme cleaved the amide bond between N-acetyl-muramic acid and l-alanine of the peptide side chain of the rigid layer (murein) of Escherichia coli. The N-acetylmuramyl-l-alanine amidase released all of the peptide side chains including those to which the lipoprotein is bound. A portion of the peptide side chains of the Micrococcus lysodeikticus murein was also hydrolysed from the polysaccharide chains. E. coli, M. lysodeikticus, Bacillus subtilis and Staphylococcus aureus were not killed by the amidase. Treatment of E. coli with EDTA or osmotic shock rendered the cells sensitive to the amidase and they were killed. Possible biological functions of the amidase are discussed.The enzyme was separated from lysozyme in human serum. Gel permeation chromatography indicated a molecular weight of the active enzyme of 82,000 while gel electrophoresis in the presence of sodium dodecyl sulfate revealed a molecular weight of 75,000. Thus, the enzyme probably consists of a single polypeptide chain. Incubation with neuraminidase rendered the amidase more basic suggesting the release of sialic acid residues. The modified glycoprotein disclosed an increased activity to murein. Enzyme activity was inhibited by p-chloromercuribenzene sulfonate and ethyleneglycol-bis(2-aminomethyl) tetraacetate (EGTA) at 1 and 0.2 mM concentration, respectively, whereas EDTA up to 5 mM was without effect. The amidase was also inactivated by agents that reduce disulfide bridges. 相似文献
13.
Mutagenicity of 5,6-dimethoxysterigmatocystin, a metabolite from Aspergillus multicolor, in the Salmonella/microsome system. 总被引:1,自引:1,他引:0
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The natural sterigmatocystin derivative, 5,6-dimethoxysterigmatocystin, was found to be a mutagen for Salmonella typhimurium strains TA98 and TA100 after metabolic activation in a mammalian microsome system. 相似文献
14.
Robert J. Kadner Knut Heller James W. Coulton Volkmar Braun 《Journal of bacteriology》1980,143(1):256-264
15.
This paper describes a highly specific method for determining urinary 17-hydroxycorticosteroids, which has been developed by (i) changing the composition of the Porter-Silber reagent and (ii) removing contaminants interfering with the color reaction by addition of sodium bisulfite to β-glucuronidase-hydrolyzed urine before extraction with solvent. For a reference method the Norymberski-Riondel (J. K. Norymberski and A. Riondel 1970, Biochem. J. 120, 493–498) gas chromatography (glc) was used: Correlation coefficient between the present method and GLC = 0.988, deviation from the theoretical regression LINE = 6.8%, and coefficient of SIMILARITY = 0.56. These results are much better than those obtained by I. Ernest, B. Håkansson, J. Lehmann, and B. Sjögren (1964, Acta Endocrinol. 46, 552–562) for the original Porter-Silber method in comparison with the chromatographic measurement of grouped and individual steroids. 相似文献
16.
17.
Norbert Volkmar Christian M GawdenBone James C Williamson Jonathon NixonAbell James A West Peter H St GeorgeHyslop Arthur Kaser Paul J Lehner 《The EMBO journal》2022,41(19)
The regulation of membrane lipid composition is critical for cellular homeostasis. Cells are particularly sensitive to phospholipid saturation, with increased saturation causing membrane rigidification and lipotoxicity. How mammalian cells sense membrane lipid composition and reverse fatty acid (FA)‐induced membrane rigidification is poorly understood. Here we systematically identify proteins that differ between mammalian cells fed saturated versus unsaturated FAs. The most differentially expressed proteins were two ER‐resident polytopic membrane proteins: the E3 ubiquitin ligase RNF145 and the lipid hydrolase ADIPOR2. In unsaturated lipid membranes, RNF145 is stable, promoting its lipid‐sensitive interaction, ubiquitination and degradation of ADIPOR2. When membranes become enriched in saturated FAs, RNF145 is rapidly auto‐ubiquitinated and degraded, stabilising ADIPOR2, whose hydrolase activity restores lipid homeostasis and prevents lipotoxicity. We therefore identify RNF145 as a FA‐responsive ubiquitin ligase which, together with ADIPOR2, defines an autoregulatory pathway that controls cellular membrane lipid homeostasis and prevents acute lipotoxic stress. 相似文献
18.
Johanna Blomqvist Thomas Eberhard Johan Schnürer Volkmar Passoth 《Applied microbiology and biotechnology》2010,87(4):1487-1497
The influence of pH, temperature and carbon source (glucose and maltose) on growth rate and ethanol yield of Dekkera bruxellensis was investigated using a full-factorial design. Growth rate and ethanol yield were lower on maltose than on glucose. In controlled
oxygen-limited batch cultivations, the ethanol yield of the different combinations varied from 0.42 to 0.45 g (g glucose)−1 and growth rates varied from 0.037 to 0.050 h−1. The effect of temperature on growth rate and ethanol yield was negligible. It was not possible to model neither growth rate
nor ethanol yield from the full-factorial design, as only marginal differences were observed in the conditions tested. When
comparing three D. bruxellensis strains and two industrial isolates of Saccharomyces cerevisiae, S. cerevisiae grew five times faster, but the ethanol yields were 0–13% lower. The glycerol yields of S. cerevisiae strains were up to six-fold higher compared to D. bruxellensis, and the biomass yields reached only 72–84% of D. bruxellensis. Our results demonstrate that D. bruxellensis is robust to large changes in pH and temperature and may have a more energy-efficient metabolism under oxygen limitation
than S. cerevisiae. 相似文献
19.
Transport across the outer membrane of Escherichia coli K12 via the FhuA receptor is regulated by the TonB protein of the cytoplasmic membrane 总被引:40,自引:0,他引:40
Summary Point mutations in the “TonB box” offhuA were suppressed by point mutations in thetonB gene, suggesting both a functional and physical interaction between the FhuA receptor protein in the outer membrane and the
TonB protein in the cytoplasmic membrane ofEscherichia coli K12. Mutations influA were classified into four types according to the extent by which they impaired mutant cells in their growth on ferrichrome
as sole iron source and in their sensitivity to the antibiotic albomycin and to colicin M. ThetonB mutation with a glutamine to leucine replacement at position 165 was less efficient in restoring the FhuA functions than
the glutamine to lysine exchange at the same position. The better the coupling between FhuA and TonB the poorer was the inhibition
of phage T1 binding to FhuA by ferrichrome. A working model is proposed in which the TonB protein assumes different conformations
in response to the energized state of the cytoplasmic membrane and thereby allosterically regulates the activity of the FhuA
receptor. This model implies an intermembrane coupling between two proteins in adjacent membranes. 相似文献
20.
Kai-Shu Ling Karen R. Harris Jenelle D. F. Meyer Amnon Levi Nihat Guner Todd C. Wehner Abdelhafid Bendahmane Michael J. Havey 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2009,120(1):191-200
Zucchini yellow mosaic virus (ZYMV) is one of the most economically important potyviruses infecting cucurbit crops worldwide. Using a candidate gene approach,
we cloned and sequenced eIF4E and eIF(iso)4E gene segments in watermelon. Analysis of the nucleotide sequences between the
ZYMV-resistant watermelon plant introduction PI 595203 (Citrullus lanatus var. lanatus) and the ZYMV-susceptible watermelon cultivar ‘New Hampshire Midget’ (‘NHM’) showed the presence of single nucleotide polymorphisms
(SNPs). Initial analysis of the identified SNPs in association studies indicated that SNPs in the eIF4E, but not eIF(iso)4E,
were closely associated to the phenotype of ZYMV-resistance in 70 F2 and 114 BC1R progenies. Subsequently, we focused our efforts in obtaining the entire genomic sequence of watermelon eIF4E. Three SNPs
were identified between PI 595203 and NHM. One of the SNPs (A241C) was in exon 1 and the other two SNPs (C309A and T554G)
were in the first intron of the gene. SNP241 which resulted in an amino acid substitution (proline to threonine) was shown
to be located in the critical cap recognition and binding area, similar to that of several plant species resistance to potyviruses.
Analysis of a cleaved amplified polymorphism sequence (CAPS) marker derived from this SNP in F2 and BC1R populations demonstrated a cosegregation between the CAPS-2 marker and their ZYMV resistance or susceptibility phenotype.
When we investigated whether such SNP mutation in the eIF4E was also conserved in several other PIs of C. lanatus var. citroides, we identified a different SNP (A171G) resulting in another amino acid substitution (D71G) from four ZYMV-resistant C. lanatus var. citroides (PI 244018, PI 482261, PI 482299, and PI 482322). Additional CAPS markers were also identified. Availability of all these
CAPS markers will enable marker-aided breeding of watermelon for ZYMV resistance. 相似文献