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. 2007 Jun 1;35(12):3945–3952. doi: 10.1093/nar/gkm357

Figure 1.

Figure 1.

Induction activity of the C-terminal Met insertion mutant TrxA-Mtip. (A) A schematic presentation of the E. coli screening strain for TetR inducing peptides is shown (10). Escherichia coli DH5α(λtet50) contains lacZ under Tet control on the chromosome. Derivatives of pWH527 or pWH1413 constitutively express LacI and the TetR variants. The TetR dimer is depicted by light gray ovals with circular DNA-binding domains. TetR controls transcription of lacZ. The peptide-expressing plasmids encode either TrxA (pWH2200) or SbmC (pWH2300) or the respective fusion protein (e.g. TrxA(C)-XTip is encoded by pWH2102-X) under control of Ptac. A TetR inducing thioredoxin-peptide fusion leads to β-Gal expression as indicated by the arrow. The respective resistance genes and origins of replication of the plasmids are indicated. (B) Sequences of Tip peptides (bold) fused C-terminal or N-terminal to TrxA and the linker between TrxA and Tip are shown in one-letter abbreviations. (C) β-Gal activities obtained with the indicated TrxA-Tip fusions in the presence and absence of IPTG are shown. Gray bars show the repressed states in the absence of IPTG. Expression of the Tip-fusion proteins was induced with 60 µM IPTG (black bars). (D) Western blots indicating the steady-state levels of Tip-fusion proteins in the presence of 60 µM IPTG. Molecular weights of marker proteins (not shown) are indicated on the left side.