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Isopropyl β-d-1-thiogalactopyranoside (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 .
In E. coli BL21(DE3) the expression of the T7-RNAP is suppressed by the constitutively expressed LacI repressor. LacI binds the lac operator, which is located downstream of the LacUV5 promoter, preventing the production of the T7-RNAP. However, upon supplementation of IPTG, the LacI repressor dissociates from the lac operator, allowing for the ...
The T7 expression system is used in the field of microbiology to clone recombinant DNA using strains of E. coli. [1] It is the most popular system for expressing recombinant proteins in E. coli. [2] By 2021, this system had been described in over 220,000 research publications. [3]
Its production may be induced by a non-hydrolyzable analog of allolactose, IPTG, which binds and releases the lac repressor from the lac operator, thereby allowing the initiation of transcription to proceed. It is commonly used in molecular biology as a reporter marker to monitor gene expression.
IPTG, a molecule similar to lactose, but with a sulfur bond that is not hydrolyzable so that E. coli does not digest it, is used to activate or "induce" the production of the new protein. Once the cells are induced, it is difficult to remove IPTG from the cells and therefore it is difficult to stop expression.
A schematic representation of the molecular mechanism involved for screening recombinant cells. The lacZ fragment, whose synthesis can be induced by IPTG, is capable of intra-allelic complementation with a defective form of β-galactosidase enzyme encoded by host chromosome (mutation lacZDM15 in E. coli JM109, DH5α and XL1-Blue strains). [4]
The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria.Although glucose is the preferred carbon source for most enteric bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of β-galactosidase. [1]
Expression of functionally active human epidermal growth factor has been done in C. glutamicum, [17] thus demonstrating a potential for industrial-scale production of human proteins. Expressed proteins can be targeted for secretion through either the general, secretory pathway (Sec) or the twin-arginine translocation pathway (Tat). [18]