Recently I tried to transform two plasmids derived from pGEX-2TK in E. coli BL21.
There were many colonies on the agar plate so I picked 8 for further analysis.
After induction by IPTG, SDS-PAGE showed half of them expressed one recombinant protein and
the other 4 expressed another recombinant protein.
It seems that the cell can only accept one plasmid.
The recombinant proteins are 59 and 70 KDa (including GST tag) and the recombinant plasmids are
about 6.1 Kbp.
Do you have any idea what happened to my experiment?
Due to the copy number of plasmid?
Many thanks for any suggestions.
