Regulation of newly evolved enzymes. IV. Directed evolution of the Ebg repressor.

Evolution of a regulated operon in the laboratory.

The evolution of new metabolic functions is being studied in the laboratory using the EBG system of E. coli as a model system. It is demonstrated that the evolution of lactose utilization by lacZ deletion strains requires a series of structural and regulatory gene mutations. Two structural gene mutations act to increase the activity of ebg enzyme toward lactose, and to permit ebg enzyme to conv...

Regulation of newly evolved enzymes. I. Selection of a novel lactase regulated by lactose in Escherichia coli.

Thirty-four lactose-utilizing strains of E. coli were selected from a lac Z deletion strain. In 31 of these, the synthesis of the newly evolved lactase is regulated by lactose. The lactase activity in all the strains is indistinguishable from the ebg(+) activity identified by Campbell, Lengyel and Langridge (1973).

Sequence of the ebgR gene of Escherichia coli: evidence that the EBG and LAC operons are descended from a common ancestor.

The sequence of ebgR, the gene that encodes the EBG repressor, was determined. There is 44% DNA sequence identity between ebgR and lacI, the gene that encodes the LAC repressor. There is also 25% identity between the amino acid sequence of lacI and the deduced amino acid sequence of ebgR. The sequence of 596 bp distal to ebgA, the structural gene for EBG beta-galactosidase, was also determined....

Down Regulation of DHFR Promoter Activity by PML Transcription Repressor

Evolutionary potential of the ebgA gene.

Twenty years ago a study was initiated (Hall and Hart1 1974) whose purposes were to understand the evolutionary potential that lay within the genome of an organism, and to understand the processes and mechanisms by which the organism could exploit that potential to adapt to new selective pressures (Hall 1990). That study exploited the ebg operon of Escherichia coli K 12. The ebg operon encodes ...