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. 2014 Dec 4;8(12):e3356. doi: 10.1371/journal.pntd.0003356

Figure 1. Schematic representation of the dual T7 promoter TcpA-A2-CTB expression plasmid pGAP31-2XT7 and amino acid sequence of the TcpA (29–199) fragment encoded by V.cholerae El Tor N16961.

Figure 1

Gene fragment tcpA (encoding residues 29–199 of mature TcpA) and gene fragment a2 (encoding the A2 polypeptide corresponding to residues 196–240 of mature CTA) were cloned in-frame and downstream of gene fragment pelB (encoding the PelB signal sequence), and the recombinant gene was expressed under control of an IPTG-inducible T7 promoter. Gene fragment ctb (encoding mature CTB) was cloned in-frame and downstream of another pelB gene fragment, and the recombinant gene was expressed under control of a second IPTG-inducible T7 promoter. The PelB signal sequences directed the TcpA-A2 fusion protein and CTB into the periplasm in E. coli, and the TcpA-A2-CTB chimera was assembled spontaneously in the periplasm from one TcpA-A2 polypeptide and five CTB polypeptides. The amino acid sequence of the TcpA fragment (residues 29–199) that is included in the TcpA-A2 fusion protein is shown at the bottom of the figure.