Bacteriophage lambda-E. coli K12 vector-host system for gene cloning and expression under lactose promoter control. II. DNA fragment insertion at the vicinity of the lac UV5 promoter.

Bacteriophage vectors derived from lambda plac5 have been constructed. Their genomes have one EcoRI restriction site which is located at the very beginning of the lac Z gene. The major part of this gene was deleted by an in vivo intramolecular recombination. These vectors allow the fusion of a gene or an operon with the beginning of the lac Z gene, placing them under the control of the lac promoter, which carries the UV5 mutation. Some of these vectors (lambda Y) also include the lac Y gene and it too is under the control of the lac promoter. The lambda YEQS, which carries the Qam73 and Sam7 mutations, as safety mutations, has been certified as a B2 (EK2) vector by the French control commission "recombinaison génétique in vitro".