Tuesday, 21 February 2012

IPTG a more effective inducer for the lac operon compared to lactose

IPTG is a substituted galactoside, where the glucose moiety of lactose is replaced by another chemical group.IPTG binds to repressor and inactivates it, but is not a substrate for β-galactosidase enzyme. IPTG is an effective inducer because of the following reasons:

1.One advantage of IPTG for in vivo studies is that it cannot be metabolized by E. coli, therefore the growth rate of cells (usually maintained with glycerol as the carbon and energy source), is not a variable in the experiment.

2. IPTG is not dependent on permease to enter the cell and is not cleaved by ßgalactosidase.So it is transported efficiently independent of whether the lacY gene is functional. And since cells don't metabolize IPTG, its concentration doesn't change during the course of an experiment.

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