- The lacUV5 promoter is a mutated version of the native E. coli lac promoter, engineered for stronger and more consistent transcriptional activity.
- It differs from the wild-type lac promoter by two point mutations in the -10 region, which improve RNA polymerase binding affinity and make transcription initiation more efficient.
- A major advantage of the lacUV5 promoter is that it is less sensitive to catabolite repression compared to the native lac promoter. This means it can remain active even in the presence of glucose, which would typically suppress expression in standard lac-controlled systems.
- Like the original lac promoter, lacUV5 is regulated by the LacI repressor and can be induced by IPTG (isopropyl β-D-1-thiogalactopyranoside), a non-metabolizable analog of allolactose.
- The lacUV5 promoter is commonly used in E. coli expression systems, especially in strains such as BL21(DE3), where it controls the expression of T7 RNA polymerase.
- Upon IPTG induction, T7 RNA polymerase is produced, which then transcribes target genes under a T7 promoter on a plasmid. The lacUV5 promoter thus serves as the primary regulatory switch in this two-step expression system, providing tighter control over when recombinant proteins are produced.
- Its strength and reduced catabolite sensitivity make it especially useful for industrial and laboratory-scale protein expression where reproducibility and yield are critical.
