Figure 43-2: Simple examples of plasmid expression vectors using lambda promoters. Upper: In each diagram the relevant elements of lambda within the plasmid vector are located within the solid segment. Transcription in pKC30 is driven from pL and is blocked by lambda repressor provided in trans (80). The resulting transcript includes nutL, the site at which N protein can interact with RNA polymerase to enable transcription to proceed beyond stop signals. A coding sequence inserted at the HpaI site will be expressed if it includes a rbs. N protein can be provided in trans following derepression of the defective cro-prophage that encodes repressor. In the presence of N protein transcription will read through the termination signal t1. Middle: Transcription in pCVQ2 is driven from pR, and repressor is provided by the cI gene (cI857) present on the plasmid (76). The cI gene is transcribed from pRM, a promoter that is autogenously regulated by lambda repressor. The lambda sequence includes the Shine-Dalgarno sequence and initiation codon of the cro gene. Lower: Transcription in pQTE is driven from the late promoter (22). Q gene product is essential for transcription from pR? to proceed through tR?. Derepression of the lac promoter activates transcription of Q. Coding sequences inserted downstream of pR? will be translated if they have a rbs. (for better image quality, click here for tif image, which may be quite large; may also require screen refreshing plus special software to view; or view larger tif in separate window)

Figure 43-1, Figure 43-2, Figure 43-3, Figure 43-4

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