How does IPTG work?
How does IPTG work?
How does IPTG work?
IPTG, which is similar to the lactose metabolite allolactose, induces the lac operon by binding to the lac repressor. Once IPTG binds to the lac repressor, a conformational change occurs, causing the lac repressor to dissociate from the lac promoter. Once the lac repressor dissociates, RNA polymerase binds to the promoter to initiate expression.
How much IPTG should be used for expression/ What concentration of IPTG should be used for expression?
Most papers recommend using between 0.1-1.0mM IPTG for expression. However, the amount you should use depends on your proteins. However, it is best to run an IPTG titration with ranges between 0.01-1.0mM and compare using SDS-PAGE to determine the optimal concentration. Something to keep in mind is higher concentrations of IPTG can cause inclusion bodies.
Why should I use IPTG over lactose?
IPTG is non-metabolizable, so its concentration remains stable and doesn’t get consumed by the bacteria.
When should I add IPTG during culture growth?
You should usually add IPTG at the mid-log phase (OD600 ≈ 0.4–0.6) to ensure cells are healthy and dividing rapidly.
Do I need to autoclave IPTG?
No—filter sterilize only. IPTG is heat-sensitive and should not be autoclaved.
Does IPTG degrade over time?
IPTG is stable when stored properly (aliquoted at -20°C, protected from light), but repeated freeze-thaw cycles should be avoided.
Can IPTG be reused after thawing?
The best practice is to use single-use aliquots of IPTG. Do not refreeze IPTG leftovers to avoid degradation or contamination.
Can IPTG be toxic to cells?
IPTG can be toxic at high concentrations or in sensitive strains. Lowering the IPTG concentration or using auto-induction media can help.
Summary Table for FAQ
Topic | Details |
What is IPTG? | Synthetic nonmetabolizable analog of lactose; lac repressor inducer |
Mechanism | Binds Lacl → allosteric release → transcription initiation |
Main uses | Blue–white screening; recombinant protein induction via lac/T7 promoters |
Host systems | DE3 strains with T7 systems (e.g. BL21(DE3) |
Typical induction | 0.1–1.0 mM final IPTG; midlog phase (OD₆₀₀=0.4–0.6) |
Protocol variants | Fast induction: 37 °C for 2–5 h vs slow: ~20 °C overnight 12–16 h |
Preparation | Powder stored at −20 °C; filtersterilized stock aliquoted |
Side effects | High concentration toxicity; inclusion bodies |
Recommendations | Conduct IPTG titration; test temperature; use aliquots; avoid refreeze |
Advantages of Aladdin IPTG | High purity, synthetic, published reliability, affordable, convenient formats |
Aladdinsci: https://www.aladdinsci.com