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KMID : 0545119920020040243
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Journal of Microbiology and Biotechnology
1992 Volume.2 No. 4 p.243 ~ p.247
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Construction of L-Threonine Overproducing Escherichia coli by Cloning of the Threonine Operon
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Lee, Jin Ho
Oh, Jong Won/Noh, Kap Soo/Lee, Hyune Hwan/Lee, Jae Heung
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Abstract
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The thr operon of Escherichia coli TF427, an α-amino-β-hydroxyvaleric acid (AHV)-resistant threonine overproducer, was cloned in a pBluescriptII KS^+ plasmid by complementation of E. coli mutants. All clones contained a common 8.8 kb HindIII-generated DNA fragment and complemented the thrA, thrB, and thrC mutants by showing that these clones contained the whole thr operon. This thr operon was subdoned in, the plasmid vectors pBR322, pUC18, and pECCG 117, an E. coli/Corynebacterium glutamicum shuttle vector, to form recombinant plasmids pBTF11, pUTF25 and pGTF18, respectively. The subcloned thr operon was shown to be present in a 6.0 kb insert. A transformant of E. coli TF125 with pBTF11 showed an 8∼11 fold higher aspartokinase I activity, and 15∼20 fold higher L-threonine production than TF125, an AHV-sensitive methionine auxotroph. Also, it was found that the aspartokinase I activity of E. coli TF125 harboring pBTF11 was not inhibited by threonine and its synthesis was not repressed by threonine plus isoleucine.
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KEYWORD
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