Figure 4. Translational control by the P. putida and P. aeruginosa ibpA 5′UTRs.

A and B. Secondary structure prediction of the P. putida ibpA and P. aeruginosa ibpA 5′UTR calculated with RNAfold [36]. Introduced point mutations are indicated. Shine-Dalgarno regions (SD) and start codons are marked. C. Temperature-dependent expression of the ibpA-bgaB fusions. β-galactosidase assays were carried out with the ibpA wild type 5′UTRs and point-mutated variants translationally fused to bgaB in E. coli DH5α. Cells were grown at 25°C to OD₆₀₀ 0.5, induced with 0.01% L-arabinose and shifted for 30 minutes to 42°C before β-galactosidase activity was measured. MU values for the Pp ibpA and the Pa ibpA-UTR (38 MU and 8 MU) at 25°C were set to 1. Activities from the mutated variants were normalized to the corresponding wild types. The average results of three independent measurements are shown with indicated standard deviations. An E. coli ibpA-bgaB fusion was used as a positive control (C1; 14 MU at 25°C) [18].