Construction and physical mapping of plasmids containing the metJBLF gene cluster of E. coli K12

In vitro recombination techniques were used to clone the E. coli metJBLF gene cluster in a plasmid vector. Several chimeric plasmids were obtained, analyzed by restriction mapping and characterized genetically. The combined results establish that the met gene cluster is contained on an approximately 5.6 kilobase segment of bacterial DNA with metL between metB and metF. The origin of metL was localized precisely by its DNA sequence and its transcription direction was established.