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IPTG is a molecular biology reagent. This compound is a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lac operon, and it is therefore used to induce protein expression where the gene is under the control of the lac operator.

Applications

At low concentration, IPTG enters cells through lactose permease, but at high concentrations (typically used for protein induction), IPTG can enter the cells independently of lactose permease.

In blue-white screen, IPTG is used together with X-gal. Blue-white screen allows colonies that have been transformed with the recombinant plasmid rather than a non-recombinant one to be identified in cloning experiments.

IPTG is used to induce expression of cloned genes under control of the lac operon. It is used in conjunction with X-Gal to determine the lac phenotype in blue/white colony screening.

IPTG is also used to differentiate recombinants from non-recombinants in cloning strategies using vectors containing the Z or Z peptide gene.

Tips

When stored as a powder at 4 °C or below, IPTG is stable for 5 years. It is significantly less stable in solution.