The araFGH operon in E. coli contains three genes that encode the proteins that make up an ABC transporter complex involved in the transport of arabinose into the cell. The operon can be activated by the cAMP-activated global transcriptional regulator CRP (CAP), which in turn is activated by the binding of cAMP to the protein. Activated CRP can bind to DNA upstream of the promoter, and can interacrt with RNA polymerase, activating transcription of the operon. The binding of cAMP occurs when the levels are high, typically in instances where glucose is lacking in the cell. The operon can also be activated by the binding of the AraC family transcriptional regulator. AraC is activated in the presence of alpha-L-arabinopyranose, which binds to the protein and allows it to bind more strongly to its binding sites upstream of the CRP binding site. In this operon, AraC can bind in four different locations, and allow the operon to be transcribed. The first gene in the operon, araF, encodes an L-arabinose-binding periplasmic protein, which is one of the five subunits making up the arabinose transporter complex. The second gene, araG, encodes the arabinose import ATP-binding protein AraG, which is likely responsible for the ATP coupling involved in the transport of arabinose. Two AraG subunits are involved in the transporter complex. The final gene, araH, encodes the L-arabinose transport system permease protein AraH, which is likely involved in the translocation of arabinose across the cell membrane. Two AraH subunits are involved in the transporter complex.

Operon: Periplasmic Binding Protein Inner Membrane Protein Controlled by araC References