Fig. 1: Principle of arabinose-inducible ATFs established in this study.
a Inducer-OFF state: In the absence of arabinose, an AraC dimer binds to the O2 and I1 half-sites, causing DNA looping, which prevents RNAP from accessing the promoter. As a result, the ATF is not expressed. Therefore, the expression of reporter FP that is controlled by the ATF is not induced. b Inducer-ON state: Externally added arabinose enters the cell via a transporter. The arabinose-bound AraC dimer changes conformation and binds the I1 and I2 half-sites of PBAD, activating the transcription of the ATF. The ATF targets its BS(s) within a synthetic promoter, controlling FP expression. The interaction of the ATF and RNAP leads to increased FP expression from the synthetic promoter compared to the OFF state26. To simplify the figure, the RBSs and terminators located, respectively, upstream and downstream of the ATF and FP are not shown. ATF artificial transcription factor; BS binding site; FP fluorescent protein; I1, I2, and O2 represent DNA binding half-sites.; PBAD, arabinose-inducible araBAD promoter; Pmin, minimal synthetic promoter containing the −35 and −10 essential elements; Pweak, weak promoter; RNAP RNA polymerase.
