The Arabinose Operon

[Thraxman]

The Arabinose Operon

O2-----||------araC------||-------O1-----||----CRP-------||---araI----||---araA---araB---araD-----

I’m trying to wrap my head around the The Arabinose Operon and I’m having some trouble visualizing what’s taking place. They say:

araO1 is an operator site. AraC binds to this site and represses its own transcription from the PC promoter.In the presence of arabinose, however, AraC bound at the araO1 operator site helps to activate expression of the PBAD promoter.

First what is a PC promoter?

They go on to explain:
araI is also the inducer site. Transcription starts at the initiator (araI). AraC bound at this site can simultaneously bind to the araO2 site to repress transcription from the PBAD promoter. In the presence of arabinose, however, AraC bound at this site helps to activate expression of the PBAD promoter.

I'm not sure where the AraC is binding to first in the presence of arabinose, the araO1 or the araI ?

They go further and explain:
CRP binds to the CRP binding site. It does not directly assist RNA polymerase to bind to the promoter in this case. Instead, in the presence of arabinose, it promotes the rearrangement of AraC when arabinose is present from a state in which it represses transcription of the PBAD promoter to one in which it activates transcription of the PBAD promoter.
What is CRP?

I wish i could find an animation for this process!
In any case, Thank you for any help you can give!

[canalon]

would this explanation from a presumably reputable source help:
http://www.nature.com/scitable/topicpag ... ffect-1009

[jonmoulton]

They've had a long slow start; it's nice to see Scitable getting some traction.