#Id: 6419
#Unit 2. Cellular Organization
When arabinose is present, AraC binds that sugar and adopts a configuration that allows it to bind DNA as a dimer to the adjacent half-sites, araI1 and araI2).
Just upstream of these is a CAP site: in the absence of glucose, CAP binds here and helps activation.
In the absence of arabinose, the araBAD genes are not expressed. This is because when not bound to arabinose, AraC adopts a different conformation and binds DNA in a different way: one monomer still binds the araI1 site, but the other monomer binds a distant half-site called araO2.
