Proposed model for the transcriptional activation of PltR and autoinduction of pyoluteorin on Plt biosynthetic operon in <i>P. aeruginosa</i> M18.

<p>(<b>A</b>)<b> </b> Thick arrows indicate activation, autoinduction, and positive regulation; thin arrows indicate biogenesis. P_L and P_R denote the promoters of <i>pltL</i> and <i>pltR</i>. P_X and P_Y are two uncharacterized promoters. The TSS is shown with +1. The LysR-type regulator PltR transcriptionally activates the <i>plt</i> operon expression by directly binding to the <i>pltLp</i> region at the indispensable palindromic <i>lys</i> box. PltR also functions as a candidate receptor of Plt. Plt, as a potential and nonessential cofactor of PltR, specifically induces the expression of the <i>pltL</i> promoter and thus the <i>plt</i> operon. (<b>B</b>) <b>The PltR protein comprise two domains:</b> the N-terminal LysR-family HTH (helix-turn-helix) DNA-binding domain and the C-terminal co-inducer binding domain (predicted by Pfam 25.0). aa, amino acids.