iptg.info
Chemical Properties.
| isopropyl-beta-D-thiogalactopyranoside | |
| MW | 238.3 |
| Formula | C9H18O5S |
| CAS | 367-93-1 |
| Further information | Wikipedia Information |
Storage and handling
The chemical will degrade in the presence of moisture and light so store in sealed container and protect from the light. iptg should be stored at -20 but warmed to room temperature prior to exposing to the air (this reduces the amount of water that the chemical will absorb from the air).
What is iptg?
This chemical is used to mimic a natural process in simple celled organism whereby the presence of lactose stimulates the cell to switch on certain genes which can metabolise the lactose. IPTG is usually used with a chemical called X-gal which work together to act as a visible chemical markers during genetic experiments.
What is the normal pathway for lactose metabolism?
The explanation below is good but high level summary of the pathway - for a more detailed explanation with helpful diagrams visit this link.
In nature bacteria can use a range of sugars to provide their energy, however each particular sugar needs a different range of proteins and enzymes which the cell must produce to break them down safely. As it would be very wasteful for cells to produce all the chemicals they need for all sugars all the time they have developed ways to only produce the necessary proteins when a sugar is available.
When lactose is in environment a few molecules will leak into the cell, where they will be partially broken down into allolactose. Allolactose actually switches on a set of genes, called the lac operon, which produce the proteins needed increase the amount of lactose entering the cell and to break it down into simple sugars.
Normally the lac operon is repressed by proteins that bind to a part of the operon, the operator, allolactose stops these repressors working thereby switching on the genes in the lac operon.
When the operon is switched on it produces proteins called permease (that transport lactose from the environment into the bacteria) and beta-galactosidase (which cuts lactose into glucose and galactose).
In nature the cell is breaking down lactose and allolactose all the the time so as soon as the lactose in the environment is used up the repressors start to work on the lac operon again and the cell stops making proteins which no longer have any use.
How does iptg interact with this pathway?
iptg mimics allolactose and switches on the lac operon, however the cell can not break iptg down so the lac operon remains permanently on. IPTG induces activity of beta-galactosidase, an enzyme that promotes lactose utilization, by binding and inhibiting the lac repressor. For more information on how iptg interacts with this pathway please refer to this lecture. IPTG is effective at concentrations in the range of 100 μM - 1.5 mM.
What is iptg used for?
In cloning experiments one of the lac operon genes, lacZ , is replaced with a gene of interest and iptg is used to switch on the inserted gene and make it produce lots of protein. iptg is also used with x-gal to select for particular genes, see the glossary under X-gal for more details.