From 2007.igem.org

According to the in vitro cross-binding data reported by Kalodimos et al. [1], We used LacI and LRLa as the upstream input signals in the first version co-repression test-bench, and used O11 (the symmetric operator of LacI) and O22(the symmetric operator of LRLa) to construct logic promoters such as BBa_I732352. But unfortunately, experimental data show that these two repressor can bind to the relative operator of each other in vivo. All measurements of co-repression based-on these two repressors are abandoned. The combination of LacI and ARL2A0203 are replaced with ARL4A0604 in the later experiments.

References

1. Kalodimos, C. G.; Bonvin, A. M. J. J.; Salinas, R. K.; Wechselberger, R.; Boelens, R. & Kaptein, R. (2002), 'Plasticity in protein-DNA recognition: lac repressor interacts with its natural operator 01 through alternative conformations of its DNA-binding domain.', EMBO J 21(12), 2866--2876.