|Overview of E. coli promoter systems useful for heterologous protein production|
|Promoters||expression Level (inductor)||Key features|
|lac promoter||Low level up to middle (IPTG)||Weak, regulated suitable for gene products at very low intracellular level.
Comparatively expensive induction.
|trc and tac promoter||Moderately high (IPTG)||High-level, but lower than T7 system. Regulated expression still possible.
Comparatively expensive induction. High basal level.
|T7 RNA polymerase||Very high (IPTG)||Utilizes T7 RNA polymerase. High-level inducible over expression.
T7lac system for tight control of induction needed for more toxic clones.
Quite expensive induction. Basal level depends on strain used (pLys).
|Phage promoter pL||Moderately high (temperature shift)||Temperature-sensitive host required. Less likelihood of "leaky" un-induced expression. Basal level; high basal level by temperatures below 30°C. No inducer.|
|tetA promoter/operator||Variable from middle to high level (anhydrotetracyclin)||Tight regulation. Independent of metabolic state. Independent of E. coli strain.
Relatively inexpensive inducer. Low basal level.
|PPBAD promoter||Variable from low to high level
|Can fine-tune expression levels in a dose-dependent manner. Tight regulation possible. Low basal level. Inexpensive inducer.|
|PBAD promoter||Variable from low to high level||Tight regulation. Low basal activity. Relatively expensive inducer.|
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