[Subjection of tetracycline resistance genes to cat promotor gene in plasmid pBR325].

A series of plasmids with tetracycline resistance genes (Tcr-operon) subjected to transcription from chloramphenicol acetyl transferase promoter (Cmr-promoter) have been constructed on the basis of plasmid pBR325, AprCmrTcr. For this purpose, a 0.8 Md fragment in pBR325 DNA bordered by unique EcoRI and HindIII restriction sites was cut out and structural genes of Tcr-operon were fused to the cat gene nucleotides corresponding to Cmr-promoter and first 72 amino acids of cat (alton, Vapnek, 1979; Marcoli et al., 1980). These plasmids with molecular weight amounting to 3 Md confer AprTcr phenotype to host cells. Tetracycline resistance can be eliminated completely by the deletion of a) Cmr-promoter; b) part of the first Tcr-operon gene.