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. Author manuscript; available in PMC: 2018 Jun 8.
Published in final edited form as: Gene. 2012 Nov 29;514(2):82–90. doi: 10.1016/j.gene.2012.11.011

Figure 1. A two-plasmid system to study TCDS in vivo.

Figure 1

This system contains two plasmids, a linear plasmid (A), i.e., pZXD51 and a circular, supercoiling-reporter plasmid (B), such as pZXD44. The linear plasmid is derived from linear coliphage N15-based plasmid pG591 and carries a laci gene under the control of the strong PlacIq promoter. E. coli cells containing pZXD51 over-express lac repressor (LacI) constitutively, which binds to the lac O1 operator (the open circle) on the supercoiling-reporter plasmids. The supercoiling-reporter plasmids were derived from plasmid pBR322 and constructed as detailed under Experimental Procedures. They harbor an IPTG-inducible promoter with different strengths and a transcription unit between the promoter and a set of 4 Rho-independent E. coli rrnB T1 terminators (winged triangles). (C)The DNA sequence of five different E. coli promoters PT7A1/O4, Ptac, PlacUV5, Plac, and PlacL8. The underlines represent the lac O1 operators.