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Summary The regulation of the synthesis of nucleoside metabolizing enzymes has been studied in cya and crp mutant strains of Escherichia coli.The synthesis of the cyt-enzymes, cytidine deaminase and uridine phosphorylase regulated by the cytR gene product, is activated by the cAMP-CRP complex. On the other hand the synthesis of the deoenzymes: deoxyriboaldolase, thymidine phosphorylase, phosphodeoxyribomutase and purine nucleoside phosphorylase, appears to be increased if an active cAMP-CRP complex cannot be formed.It also seems that nucleosides serve as poor carbon sources for cya and crp mutants; this could not solely be explained by low levels of nucleoside metabolizing enzymes nor by a deficiency in nucleoside uptake. Addition of casamino acids stimulated the growth of cya and crp mutants, with nucleosides as carbon sources. When grown on glucose and casamino acids growth could be stimulated by adenine and hypoxanthine nucleosides; these results suggest an impaired nitrogen metabolism in cya and crp mutants.Abbreviations and Symbols cAMP
cyclic adenosine 3:5-monophosphate
- CRP
cAMP receptor protein. Genes coding for: adenyl cyclase
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cya
cAMP receptor protein
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crp
cytidine deaminase
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cdd
uridine phosphorylase
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udp
thymidine phosphorylase
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tpp
purine nucleoside phosphorylase
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pup; cytR
regulatory gene for cdd, udp, dra, tpp, drm, and pup
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deoR
regulatory gene for dra, tpp, drm, and pup 相似文献
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Thorsten Pfirrmann Ashwin Lokapally Claes Andréasson Per Ljungdahl Thomas Hollemann 《PloS one》2013,8(6)
Modern biology research requires simple techniques for efficient and restriction site-independent modification of genetic material. Classical cloning and mutagenesis strategies are limited by their dependency on restriction sites and the use of complementary primer pairs. Here, we describe the Single Oligonucleotide Mutagenesis and Cloning Approach (SOMA) that is independent of restriction sites and only requires a single mutagenic oligonucleotide to modify a plasmid. We demonstrate the broad application spectrum of SOMA with three examples. First, we present a novel plasmid that in a standardized and rapid fashion can be used as a template for SOMA to generate GFP-reporters. We successfully use such a reporter to assess the in vivo knock-down quality of morpholinos in Xenopus laevis embryos. In a second example, we show how to use a SOMA-based protocol for restriction-site independent cloning to generate chimeric proteins by domain swapping between the two human hRMD5a and hRMD5b isoforms. Last, we show that SOMA simplifies the generation of randomized single-site mutagenized gene libraries. As an example we random-mutagenize a single codon affecting the catalytic activity of the yeast Ssy5 endoprotease and identify a spectrum of tolerated and non-tolerated substitutions. Thus, SOMA represents a highly efficient alternative to classical cloning and mutagenesis strategies. 相似文献
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Milberg Per Bergman Karl-Olof Glimskär Anders Nilsson Sigrid Tälle Malin 《Plant Ecology》2020,221(7):577-594
Plant Ecology - Management of semi-natural grasslands is essential to retain the characteristic diversity of flora and fauna found in these habitats. To maintain, restore or recreate favourable... 相似文献
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Özaslan Ahmet Kayhan Gülsüm İşeri Elvan Ergün Mehmet Ali Güney Esra Perçin Ferda Emriye 《Molecular biology reports》2021,48(11):7371-7378
Molecular Biology Reports - Copy number variants (CNVs) play a key role in the etiology of autism spectrum disorder (ASD). Therefore, recent guidelines recommend chromosomal microarrays (CMAs) as... 相似文献
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