Figure 2.

Construction of plasmid for expression of EI-N for in vivo experiments. The vector pSYX39 (15) contains the pSC101 origin of replication that is compatible with a number of other origins of replication; the vector was cut with BamHI. A DNA fragment was inserted into the vector that encodes a partially truncated EI-N isolated from p9C; the fragment contained the pT7 promoter at the 5′ terminus. The truncation at the 3′ terminus was corrected by cutting p9C with XbaI and HindIII, isolating the fragment, and by inserting it into pSXEI-NΔ, which had also been cut with the two restriction enzymes. The plasmid pSXEI-N contained the gene encoding all EI-N under the control of the pT7 promoter, the Cm^r gene, and the desired origin of replication.