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. 2022 Jun 1;119(24):e2203176119. doi: 10.1073/pnas.2203176119

Fig. 2.

Fig. 2.

VtrA/VtrC T3SS2 virulence regulon is homologous to ToxR/ToxS. (A) The VtrA/VtrC structure (PDB: 5kew) depicted in cartoon adopts an obligate heterodimer of the periplasmic VtrA (green) and VtrC (blue) that transmits an input signal from VtrC-bound bile acid (black stick) through the membrane (gray) via the TMH (yellow cylinder) attached to the N-terminal VtrA DNA-binding HTH (orange sphere). (B) The VtrC gene (green arrow) encoding the coregulator is downstream from the VtrA gene (blue arrow) encoding the transcription factor in an overlapping operon that is arranged similarly to the genes of the ToxR (green arrow) and ToxS (blue arrow) operon. (C) The labeled VtrA periplasmic domain, colored in rainbow from the N terminus (blue) to the C terminus (red), adopts the same fold as the labeled ToxR periplasmic domain (PDB: 6utc). (D) The labeled VtrC periplasmic domain that binds the bile acid TDC (black stick) adopts the same fold as the predicted ToxS structure model.