Transcriptional Activation of Multiple Operons Involved in para-Nitrophenol Degradation by Pseudomonas sp. Strain WBC-3.

　　 Zhang WM, Zhang JJ, Jiang X, Chao H, Zhou NY.

       Appl Environ Microbiol. 2014 Oct 17. pii: AEM.02720-14.

　    Abstract

　　Pseudomonas sp. strain WBC-3 utilizes para-nitrophenol (PNP) as a sole carbon and energy source. The genes involved in PNP degradation are organized in the following three operons: pnpA, pnpB and pnpCDEFG. How the expression of the genes is regulated is unknown. In this study, a LysR-type transcriptional regulator (LTTR) is identified to activate the expression of the genes in response to the specific inducer PNP. While the LTTR coding gene pnpR was found to be not physically linked to any of the three catabolic operons, it was shown to be essential for the growth of strain WBC-3 on PNP. Furthermore, PnpR positively regulated its own expression, which is different from the function of classical LTTRs. A regulatory binding site (RBS) with 17-bp imperfect palindromic sequence [GTT-N11-AAC] was identified in all pnpA, pnpB, pnpC and pnpR promoters. Through electrophoretic mobility shift assays and mutagenic analyses, this motif was proven to be necessary for PnpR binding. This consensus motif is centered at positions approximately -55 bp relative to the four transcriptional start sites (TSSs). The RBS integrity was required for both high-affinity PnpR binding and transcriptional activation of pnpA, pnpB and pnpR. However, this integrity was only essential for high-affinity PnpR binding to the promoter of pnpCDEFG but not for its activation. Intriguingly, unlike other LTTRs studied, no change in length of the binding regions with promoters pnpA and pnpB by PnpR was observed after the addition of the inducer PNP in DNase I footprinting.

　　http://www.ncbi.nlm.nih.gov/pubmed/25326309