| abstract |
Novel plasmidic expression vehicles and methods of using them in the production of useful polypeptides by recombinant bacteria are described. The plasmids employ a tryptophan promoter-operator system from which the attenuator region ordinarily present has been deleted. Bacteria containing-the plasmids can accordingly be repressed by the addition of tryptophan against expression of desired polypeptides coded for by inserted genes while they are grown to levels suitable for industrial-scale production. Additive tryptophan may then be withdrawn, essentially derepressing the pathway and permitting efficient production of the desired product in high yield. |