E. coli PxylA Repressing Vector pMMEc4

pMMEc4 is a helper plasmid for enabling the repression of the PxylA promoter of a second E. coli/ Bacillus shuttle vector. pMMEc4 replicates in E. coli and carries the xylR gene under control of arabinose PBAD promoter.

The construction of expression vectors for Gram-positive bacteria is often done by using shuttle vectors (e.g., E. coli / B. megaterium). E. coli is a common host for molecular cloning as transformation is fast and simple. In the case of genes encoding toxic products, it is essential to prevent any expression within E. coli during cloning procedures. The xylose inducible xylA / xylR induction system is not very tightly regulated in E. coli. It shows some degree of expression even without addition of an inducer. The vector pMMEc4 was constructed as a helper plasmid for preventing any expression from the xylA promoter in E. coli.