How does IPTG work ? - (Nov/06/2005 )

Hey guys,
I was wondering of someone could tell me, how does IPTG induce the protein expression. I am trying to express the Scrapie Prion protein PrP in E coli. I know that the IPTG is an artificial inducer, however, I understand that it would induce the production of enzyme to metabolise IPTG but how does it start the expression of my protein of interest.
Thanks in adavance for your answers.

stan

as i understand it IPTG it's a non fermentable analog of lactose and inactivates the lac repressor. in bacteria which utilise lactose, their lactose metabolising genes are in an operon which is under the control of a promoter which is usually repressed in the absence of lactose. when lactose is added to the medium it binds to and relieves the repression allowing expression of the genes involved.
so plasmids with promoters based on the lac operon can be induced when you add IPTG as it behaves like lactose removes the repression on their expression without getting inactivated itself
don't know if i made it clear enough . hope it gives you the idea though