Animal Biotechnology

EXPRESSION VECTORS WITH STRONG PROMOTERS

• The main function of an expression vector is to yield the product of a gene- usually, the more product the better.
• Therefore, expression vectors are ordinarily equipped with very strong promoters; the rationale is that the more mRNA that is produced, the more protein product will be made.
• One such strong promoter is the trp (tryptophan operon) promoter.  It forms the basis for several expression vectors.  It has a trp promoter/operator region, followed by a ribosome binding site, and can be used directly as an expression vector by inserting a foreign gene into the ClaI site.
• Alternatively, the trp control region can be made “portable” by cutting it out with ClaI and HindIII and inserting it in front of a gene to be expressed in another vector