[Decrease in the level of DeoR-dependent repression of the deo operon as a result of integration of foreign DNA...

Two heterologous DNA fragments encoding the genes Kanr and cat were integrated into the regulatory region of the deo operon of Escherichia coli, located in a recombinant plasmid. As a result, plasmids pD5K and pD5C were obtained, in which the distance between the deoO1 and deoO2 operators increased from 599 bp in the deo operon of the wild type to 2019 and 1398 bp in case of integration of Kanr and cat, respectively. Then, linearized DNA of plasmids pD5K and pD5C was incorporated into the deo locus of the chromosome of E. coli through homologous recombination by the use of a recipient strain recBC sbcB. The constructed strains contained insertions in the interoperator region of the deo operon. Expression of the deo operon was studied in these strains, on a different genetic background with respect to the genes deoR, cytR, and cyaA. An increase in the interoperator distance was shown to increase the basal level of gene expression of the deo operon and to disturb cooperative interaction of the DeoR repressor and operator sites.