REGULATION OF NEWLY EVOLVED ENZYMES. IV. DIRECTED EVOLUTION OF THE EBG REPRESSOR
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ABSTRACT In Escherichia coli, the wild-type repressor of ebg (evolved β-galactosidase) enzyme synthesis, specified by the ebgR + gene, responds very weakly to lactulose (fructose-β-D-galactopyranoside). Selection for a functional repressor that responds strongly to lactulose as an inducer reveals the existence of ebgR+L mutants, which occur spontaneously at a frequency of about 2 x 10-10. ebgR+L mutants are pleiotropic in that they specify ebg repressor with a greatly increased response to lactulose, lactose, galactose-arabinoside and methyl-galactoside as inducers. Selection of ebgR+L mutants is discussed within the framework of directed evolution of a regulatory function.
2014 ◽
Vol 58
(10)
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pp. 6024-6031
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2003 ◽
Vol 69
(5)
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pp. 3020-3023
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