[Construction of promoter-probe vectors on the basis of a modified beta-galactosidase gene of Escherichia coli].

Plasmid-based promoter-probe vectors pPV4 and pPV5 have been constructed which are useful for comparing the relative efficiencies of bacterial promoters. The vectors utilize the beta-galactosidase (lacZ) gene of E. coli as an indicator gene. The latter was modified using synthetic DNA fragments. The promotor-probe system contains the ampicillin resistance gene and the origin of replication of plasmid pBR322. The plasmids pPV4 and pPV5 carry clustered unique restriction sites usable for promoter insertions, and SD sequence. A synthetic DNA fragment corresponding to transcription terminator was inserted downstream the lacZ gene. Presence of the terminator made it possible to clone strong promoters controlling transcription of the lacZ gene. To prevent any undesired promotor effect, the plasmid pPV5 has also second synthetic terminator upstream from the polylinker sequence. Using this promoter-probe system, relative efficiencies of a series of synthetic promoters, including PL promoter of phage lambda and its mutant, gene X promotor of phage fd and several model statistic promoters, have been compared.