[Construction of the hybrid crp-lac operon and study of the role of CRP-cAMP complex in its regulation in Escherichia coli].

Phage Mu d1(Ap,lac) was used to construct the hybrid crp-lac operon in Escherichia coli cells possessing crps mutation which increases sensitivity of bacterial growth to exogenous cAMP. Transcription of the structural lac genes in this hybrid operon was initiated from the promoter region of the crp gene. By measuring levels of beta-galactosidase enzyme, the maximal transcription of the crp gene was obtained in strains with cya or crp mutations causing inactivation of the CRP - cAMP complex. Restoration of cya+crp+ genotype resulted in 5 to 7 times decrease of the lacZ gene activity. At the concentration of exogenous cAMP which induces catabolic derepression in the wild-type strain, the expression of crp-lac operon increased 2-3 times. Using F'ts114lac-mediated chromosome mobilization, the direction of transcription of the crp gene was found to be counterclockwise, relative to the E. coli genetic map.