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  • Biochemistry and Biotechnology  (2)
  • Folic acid  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 250 (1996), S. 277-285 
    ISSN: 1617-4623
    Keywords: Key words Gonococcus ; Folic acid ; Dihydrofolate synthetase ; Folylpolyglutamate synthetase ; One-carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The gene coding for folylpoly-(γ)-glutamate synthetase (FPGS)-dihydrofolate synthetase (DHFS) of Neisseria gonorrhoeae (Ngo) has been cloned by functional complementation of an Escherichia coli folC mutant (SF4). The sequence encodes a 224-residue protein of 46.4 kDa. It shows 46% identity to the E. coli FPGS-DHFS and 29% identity to the FPGS of Lactobacillus casei. Sequence comparisons between the three genes reveal regions of high homology, including ATP binding sites required for bifunctionality, all of which may be important for FPGS activity. In contrast to L. casei FPGS, the E. coli and Ngo enzymes share some additional regions which may be essential for DHFS activity. The products of Ngo folC and flanking genes were monitored by T7 promoter expression. Interestingly, deletion of the upstream folI gene, which encodes a 16.5 kDa protein, abolishes the capacity of folC to complement E. coli SF4 to the wild-type phenotype. The ability to complement can be restored by folI provided in trans. Unlike folC mutants, gonococcal folI mutants are viable and display no apparent phenotype. Thus, in contrast to E. coli, Ngo folC is expressed at a sufficiently high level from its own promoter, in the absence of FolI. This study provides the first insights into the genetic complexity of one-carbon metabolism in Ngo.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 927-939 
    ISSN: 0006-3592
    Keywords: CHO cells ; human secreted alkaline phosphatase ; tumor suppressor genes ; green fluorescent protein ; cell cycle ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have established a novel production process which allows up to fourfold higher production of a model secreted protein, the human secreted alkaline phosphatase (SEAP), in Chinese hamster ovary (CHO) cells. A cytostatic production phase is established in which cell proliferation is inhibited or completely abolished. Such a cytostatic production phase is established by overexpression of the tumor suppressor genes p21, p27, or p53175P (a p53 mutant showing specific loss of apoptotic function) under transcriptional control of a tetracycline-repressible promoter (PhCMV*-1). In order to minimize complications due to possible clonal variation of selected, stable cell lines, our investigations are based on transiently transfected subpopulations, that have become a useful tool in industrial R&D. These subpopulations have been selected by flow cytometry for the expression of genes encoded on a dicistronic expression vector. These vectors contain a dicistronic expression unit consisting of the genes encoding the green fluorescent protein (GFP) or SEAP, followed by one of the cytostatic genes p21, p27 or p53175P encoded by the second cistron. p21, p27 as well as p53175P block the cell cycle of CHO cells in the G1-phase for a prolonged period. However, these G1-arrested cells remain viable and proliferation proficient upon repression of expression of the cytostatic gene. All three of the cytostatic genes studied provided similar regulation of proliferation, and also similar enhancements in SEAP production, suggesting that higher productivity may be a general and intrinsic feature of G1-phase arrested CHO cells. Overall productivity is most likely enhanced because growth-arrested cells do not need to devote cellular resources to biomass production. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:927-939, 1997.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 1-10 
    ISSN: 0006-3592
    Keywords: pTRIDENT ; tricistronic expression vectors ; gene expression ; mammalian cells ; tetracycline-responsive promoter ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We constructed tricistronic expression vectors for the simultaneous and coordinated expression of three independent genes in mammalian cells. One single promoter allows high level and, in some vectors, adjustable transcription of all three cistrons. Whereas the first cistron is translated in a cap-dependent manner, the subsequent ones utilize intercistronic regions of viral origin such as the internal ribosomal entry site of poliovirus or the cap-independent translation enhancer of encephalomyocarditis virus for enhanced translation. Three multiple cloning sites with a total of up to 18 unique restriction sites allow sequential cloning of the genes of interest. The modular structure of this pBluescript®-based high copy number vector system allows straightforward movement of individual cistrons among members of the pTRIDENT family, and facilitates their combination with existing expression vectors. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 1-10, 1998.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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