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 p_L and is blocked by lambda repressor provided in trans (80). The resulting transcript includes nut_L, 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 p_R, and repressor is provided by the cI gene (cI857) present on the plasmid (76). The cI gene is transcribed from p_RM, 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 p_R? to proceed through t_R?. Derepression of the lac promoter activates transcription of Q. Coding sequences inserted downstream of p_R? 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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