High level expression of porcine growth hormone in Escherichia coli from an expression vector containing bacteriophage λ P_L and N gene untranslated region

An Escherichia coli expression vector, pG408N containing a P_L promoter and the upstream untranslated region of the N gene of bacteriophage λ has been constructed. We have designed a Pvull site immediately behind the untranslated region. A DNA fragment starting with an initiation codon ATG could be inserted into this site for expression. This vector also contains 7 additional cloning sites downstream from the Pvull site. A gene could be cloned into one of these sites and the 5′ sequence of this gene could be modified with synthetic oligonucleotides and ligated to the Pvull for the purpose of increasing gene expression. We have also cloned the λ cl gene into a p15A plasmid. Cotransformation of this plasmid with the expression vector allows the cloning vector pG408N to be used in any E. coli strain. Using this system, we were able to express porcine growth hormone to approximately 35% of total proteins in E. coli DH5α.