Isopropyl-β-D-thiogalactopyranoside (IPTG) is the isopropyl thioglycoside of D-Galactose. This synthetic carbohydrate is widely used in recombinant protein expression, and therefore is one of the most commonly utilized reagents in molecular biology.

In nature, the lac operon is an essential element of the lactose metabolism of many enteric bacteria such as Escherichia coli. However, the main regulating elements of the lac operon, LacI (lac repressor) and LacO (lac operator), are also important tools in biotechnology, where they find widespread use in controlling the recombinant expression of proteins in E. coli and other bacteria. To this end, the DNA sequence of a protein of interest (POI) is usually cloned into a high copy-number plasmid containing the lac promoter. Bacterial cells are then transformed using the recombinant plasmid. Suitable selection processes ensure that only cells carrying the recombinant plasmid are used for further steps. In order to induce heterologous protein expression, IPTG is added to the fermentation medium as a gratuitous inducer of the gene under the control of the LacI/LacO system.

IPTG, a structural analogon of allolactose, binds to the lac repressor, allosterically causing a conformational change which leads to the dissociation of the repressor from the lac operator. This allows RNA polymerase to bind to the promoter region of the lac operon and gene expression to commence.

Since IPTG as a thioglycoside is stable towards hydrolysis by β-galactosidases, its concentration within bacterial cells remains relatively constant, thereby facilitating a continuous expression of the protein of interest.

➔ Iris Biotech offers IPTG in a purity of min. 99% for your convenience. IPTG (dioxane grade) GBB1343