Improved plasmid vectors with a thermoinducible expression and temperature-regulated runaway replication.
Improved expression vectors have been constructed which are derived from runaway-replication mutants of plasmid R1 and carry the strong leftward promoter (pL) of bacteriophage lambda. The activity of this promoter is controlled by a temperature-sensitive repressor, product of the phage gene cI cloned on a compatible plasmid. Heat induction leads to amplification of the plasmid copy number and at the same time turns on the promoter. At a short distance downstream from the promoter, unique EcoRI, BamHI, XbaI and HindIII sites are present. This system was used for high level expression of the T4 DNA-ligase gene; 3 h after induction the ligase amounted to about 20% of total cellular protein.
D010582:Bacteriophage lambda / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D005784:Gene Amplification; D005822:Genetic Vectors; D009154:Mutation; D009876:Operon; D010957:Plasmids; D012093:Replicon; D013045:Species Specificity; D013696:Temperature