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. 2014 Jul 31;6(8):2239–2255. doi: 10.3390/toxins6082239

Figure 3.

Figure 3

Schematic representation of the NprR-NprX QS system, its regulation and its activity. The product of the nprX gene is a 43 amino-acid peptide. NprX is secreted, probably through the Sec machinery and processed via an uncharacterized mechanism. The physiological form of NprX has not been determined. However, the minimal active form is seven amino-acids long. It is imported in the cell via the oligopeptide permease Opp and presumably another oligopeptide permease system. Once inside the cell, NprX binds to NprR allowing it to activate the expression of at least 41 genes composing the NprR regulon. Transcription of nprR is activated by PlcR-PapR and is under the negative control of CodY. nprX is co-transcribed with nprR, but also possesses a promoter under the control of SigH and SigE.