Construction and expression of a hybrid plasmid containing the Escherichia coli thrA and thrB genes

In vitro recombination techniques were used to clone the Escherichia coli thrA and thrB structural genes in the plasmid vector pBR322. The chimeric plasmid was analyzed and characterized genetically, by restriction mapping and DNA sequencing. The limited expression of the threonine biosynthetic enzymes in the strain carrying the recombinant plasmid is discussed.