Fig. 1

Schematic of GFPmut3.1 expression cartridges controlled by seven different promoter/operator combinations. The cartridges were integrated into the attTN7 site (indicated with<pointed brackets>) of the E. coli BL21 chromosome, or they were cloned into the pET30a-cer vector (indicated with round brackets (), but not shown in this figure). In two promoter/operator combinations, the wild-type lacI promoter (B, black) was exchanged with the lacI^Q promoter (BQ, red). LacO1* is a 2-bp truncated version of wild-type lacO1. Sym-lacO is the perfectly symmetric lacO. The native, initially transcribed sequence of the A1 promoter, is labeled +1 T7A1 +20. Transcription is terminated by tZENIT (tZ) [27]. The BL21(DE3) T7 expression system (B3<T7>) is used as a reference. The BQ-wt carried the wild-type sequence, with the lacI^Q promoter