I've been trying to express two proteins in the BL21(DE3) strain of E. coli.
One gene is in a pCR2.1 vector and the other in a pET-expression vector. When I induce with IPTG and run on an acrylamide gel I only get the protein encoded in the pCR2.1 construct. If I transform the BL21(DE3) cells with each vector independently (only one of the plasmids in the cells) I can get expression for either protein.
Does anyone have any Idea why I wouldn't be able to induce expression from the pET vector in the double plasmid strain but can induce expression from either vector in single plasmid strains?