The Y233 gatekeeper of DmpR modulates effector-responsive transcriptional control of σ 54 -RNA polymerase.

DmpR is the obligate transcriptional activator of genes involved in (methyl)phenol catabolism by Pseudomonas putida. DmpR belongs to the AAA+ class of mechano-transcriptional regulators that employ ATP-hydrolysis to engage and remodel σ54 -RNA polymerase to allow transcriptional initiation. Previous work has established that binding of phenolic effectors by DmpR is a prerequisite to relieve inter-domain repression and allow ATP-binding to trigger transition to its active multimeric conformation, and further that a structured inter-domain linker between the effector- and ATP-binding domains is involved in coupling these processes. Here we present evidence from ATPase and in vivo and in vitro transcription assays that a tyrosine residue of the inter-domain linker (Y233) serves as a gatekeeper to constrain ATP-hydrolysis and aromatic effector-responsive transcriptional activation by DmpR. An alanine substitution of Y233A results in both increased ATPase activity and enhanced sensitivity to aromatic effectors. We propose a model in which effector-binding relocates Y233 to synchronise signal-reception with multimerisation to provide physiologically appropriate sensitivity of the transcriptional response. Given that Y233 counterparts are present in many ligand-responsive mechano-transcriptional regulators, the model is likely to be pertinent for numerous members of this family and has implications for development of enhanced sensitivity of biosensor used to detect pollutants. This article is protected by copyright. All rights reserved.