Lac operon

[TheAlchemist]

I'm trying to learn more about the Lac operon, and I am confused regarding a few thing. (sorry if this is the wrong section)

 

IPTG is a known inducer of the lac operon, which can be used instead of allolactose. My question regarding IPTG is as follows; does IPTG lead to transcription of the Lac operon or only the removal of the lac repressor? Because as I understand it, cAMP is needed as well, in order to bind the CAP activator to the CAP-binding site, so that RNA Polymerase can be recruited to the operon. So if I had glucose and IPTG, would the operon still be transcribed, since glucose leads to decrease in cAMP concentration.

 

The second question is regarding Glycerol; if it is used instead of lactose, would I still have transcription of the lac operon? Since there is no inducer to bind to the lac repressor, with glycerol I only have cAMP, is that enough?

 

Thank you in advance for all the help!

[ecoli]

I'm trying to learn more about the Lac operon, and I am confused regarding a few thing. (sorry if this is the wrong section)

 

IPTG is a known inducer of the lac operon, which can be used instead of allolactose. My question regarding IPTG is as follows; does IPTG lead to transcription of the Lac operon or only the removal of the lac repressor?

IPTG binds to and represses the lac operon repressor and does so competitively with allolactose.

 

Because as I understand it, cAMP is needed as well, in order to bind the CAP activator to the CAP-binding site, so that RNA Polymerase can be recruited to the operon.

So if I had glucose and IPTG, would the operon still be transcribed, since glucose leads to decrease in cAMP concentration.

 

in high glucose, you only get low (basal) expression,with low lactose concentrations (because the repressor is off but there's no cAMP + CAP to recruit RNAPs.). IPTG has the same effect of removing the repressor, but in high glucose will only result in basal lac operon transcription.

 

The second question is regarding Glycerol; if it is used instead of lactose, would I still have transcription of the lac operon? Since there is no inducer to bind to the lac repressor, with glycerol I only have cAMP, is that enough?

 

Thank you in advance for all the help!

 

Glycerol can be converted into glucose, so it should be able to effect lac transcription, but I suppose it depends on what cells you're using (some may lack this conversion pathway).