xylR encodes the plasmid-borne TOL transcriptional regulator XylR, a 566 aa NtrC-like enhancer-binding activator that senses aromatic effectors and uses ATP-dependent multimerization plus sequence-specific DNA binding to activate the sigma54-dependent Pu and Ps promoters of the xyl upper-pathway system and the downstream xylS regulator. The curated reviewed accession (P06519) belongs to the pWW0 system in the Pseudomonas putida mt-2 lineage (taxon 303), not the native KT2440 chromosome; this PSEPK folder should therefore be interpreted as a KT2440/pWW0-context review rather than a chromosomal KT2440 gene review.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005524 ATP binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: ATP binding is mechanistically credible for XylR because the protein contains the canonical AAA+/sigma54 activator core and UniProt annotates explicit ATP-binding residues. The 1998 promoter-switch paper further shows that ATP enhances active XylR multimerization at the UAS. However, ATP binding is a generic mechanistic property rather than the most informative description of the evolved role of this regulator. Supporting Evidence: file:PSEPK/xylR/xylR-uniprot.txt FT BINDING 263..270 file:PSEPK/xylR/xylR-uniprot.txt FT /ligand="ATP" PMID:9489676 The addition of ATP, known to trigger multimerization of the regulator at the UAS, enhanced the repression of Pr by XylR file:PSEPK/xylR/xylR-deep-research-falcon.md use a **central AAA+ ATPase domain** to couple ATP hydrolysis to remodeling of the Ο54βRNAP complex |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000002 | MODIFY | Summary: This annotation captures the right general process class but is too broad. XylR is primarily a positive activator of the sigma54-dependent Pu and Ps promoters of the TOL system, although activated XylR also contributes to repression of the divergent Pr promoter. The more specific child term positive regulation of DNA-templated transcription better reflects the main curatable biology. Proposed replacements: positive regulation of DNA-templated transcription Supporting Evidence: PMID:2993247 The xylR gene is a regulatory gene on the TOL plasmid, which acts in a positive manner on xyl operons for degradation of toluene and xylenes in Pseudomonas putida. PMID:9489676 The mechanism by which XylR, the toluene-responsive activator of the sigma54-dependent Pu and Ps promoters of the Pseudomonas TOL plasmid pWW0, downregulates its own sigma70 promoter Prhas been examined. file:PSEPK/xylR/xylR-deep-research-falcon.md it is a **signal-responsive transcriptional regulator** that activates transcription of genes enabling catabolism of aromatic hydrocarbons file:PSEPK/xylR/xylR-deep-research-falcon.md It activates the **Pu** and **Ps** promoters |
| GO:0043565 sequence-specific DNA binding | IEA GO_REF:0000002 | ACCEPT | Summary: This is a core XylR function. The C-terminal D domain carries the DNA-binding structure/HTH motif, and activated XylR binds upstream activating sequences that overlap the divergent Pr/Ps control region to regulate transcriptional switching. Falcon deep research independently corroborates that the C-terminal D domain binds UAS via an HTH-type motif and that XylR acts at a distance through DNA looping, consistent with the canonical sigma54 bEBP enhancer architecture. Supporting Evidence: PMID:3169574 The C-terminal region (aa 515-558) has a putative DNA-binding structure. file:PSEPK/xylR/xylR-uniprot.txt FT DNA_BIND 534..553 PMID:9489676 The addition of ATP, known to trigger multimerization of the regulator at the UAS, enhanced the repression of Pr by XylR file:PSEPK/xylR/xylR-deep-research-falcon.md D domain (C-terminus):** DNA binding to upstream activating sequences (UAS), typically via an HTH-type motif file:PSEPK/xylR/xylR-deep-research-falcon.md XylR binds UAS sites and can act at a distance, often requiring DNA looping and bending |
| GO:0141097 ligand-modulated transcription activator activity | TAS PMID:9489676 Activation of the toluene-responsive regulator XylR causes a... | NEW | Summary: XylR is not merely a generic DNA-binding protein; it is an aromatic-effector-responsive transcriptional activator. Aromatic induction triggers ATP-dependent multimerization and activation of sigma54-dependent target promoters, which matches ligand-modulated transcription activator activity better than the seeded GOA set. Falcon deep research adds the mechanistic basis, in which the N-terminal A domain binds aromatic effectors and represses the central activation domain until inducer binding, and deletion of the A domain yields constitutive activity, confirming ligand-modulated (effector-gated) activator behavior. Supporting Evidence: PMID:9489676 The mechanism by which XylR, the toluene-responsive activator of the sigma54-dependent Pu and Ps promoters of the Pseudomonas TOL plasmid pWW0, downregulates its own sigma70 promoter Prhas been examined. file:PSEPK/xylR/xylR-uniprot.txt In the CC presence of m-xylene or m-methylbenzyl alcohol XylR activates both the file:PSEPK/xylR/xylR-deep-research-falcon.md The N-terminal A domain is described as binding aromatic effectors and repressing the central activation domain until inducer binding file:PSEPK/xylR/xylR-deep-research-falcon.md Deletion of the N-terminal region (e.g., removal of the A domain) yields **constitutive activity** file:PSEPK/xylR/xylR-deep-research-falcon.md XylR then uses **ATP binding/hydrolysis**, oligomerization, and contact with **Ο54-RNAP** |
| GO:0042203 toluene catabolic process | TAS PMID:2993247 Determination of the transcription initiation site and ident... | NEW | Summary: xylR is required for expression of the TOL xyl operons that drive toluene assimilation/catabolism. This is the appropriate specific biological-process context for the regulatory role of XylR. Supporting Evidence: PMID:2993247 The xylR gene is a regulatory gene on the TOL plasmid, which acts in a positive manner on xyl operons for degradation of toluene and xylenes in Pseudomonas putida. PMID:16085802 Toluene degradation in Pseudomonas putida KT2440 pWW0 plasmid is subjected to catabolite repression. file:PSEPK/xylR/xylR-deep-research-openai.md XylR is the master regulator of the TOL plasmid *pWW0* upper pathway, which governs the initial **oxidative catabolism of toluene and xylenes** file:PSEPK/xylR/xylR-deep-research-falcon.md it activates the **Pu promoter** driving the **upper operon** and activates Ο54-class promoter **Ps1** to induce **xylS** file:PSEPK/xylR/xylR-deep-research-falcon.md XylR is described as the principal/master regulator in the TOL plasmid network controlling degradation of **toluene and xylene isomers** |
| GO:0042184 xylene catabolic process | TAS PMID:2993247 Determination of the transcription initiation site and ident... | NEW | Summary: The same regulatory logic applies to xylene degradation, since the xylR-controlled TOL operons mediate degradation/assimilation of xylenes as well as toluene. This process term is specific and well supported by the foundational xylR literature. Supporting Evidence: PMID:2993247 The xylR gene is a regulatory gene on the TOL plasmid, which acts in a positive manner on xyl operons for degradation of toluene and xylenes in Pseudomonas putida. PMID:20529863 In Pseudomonas putida, the expression of the pWW0 plasmid genes for the toluene/xylene assimilation pathway (the TOL pathway) is subject to complex regulation in response to environmental and physiological signals. file:PSEPK/xylR/xylR-deep-research-falcon.md Native effectors include **toluene and xylene isomers** |
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Download this section (compressed HTML)Q: Should this review remain in the PSEPK project bucket even though the reviewed accession is the plasmid-borne taxon 303 xylR protein rather than a native KT2440 chromosomal gene?
Q: Do GO curators want a separate annotation strategy for XylR-mediated autorepression of Pr, or is capturing the dominant positive activation of Pu/Ps sufficient?
Experiment: Compare WT XylR and ATP-site mutants in KT2440(pWW0) or mini-TOL reporter strains across toluene, m-xylene, benzyl alcohol, and m-methylbenzyl alcohol and measure Pu, Ps, and Pr outputs.
Hypothesis: Aromatic effector binding and ATP-dependent multimerization jointly determine XylR promoter selectivity and output strength.
Type: reporter assay
Experiment: Perform ChIP-qPCR or DAP-seq for XylR with and without aromatic inducer and test occupancy at Pu/Ps/Pr plus additional candidate TOL control regions.
Hypothesis: XylR directly occupies the known UAS elements at the divergent Pr/Ps control region in an effector-dependent manner.
Type: DNA binding assay
Experiment: Measure TOL promoter activity and XylR protein levels in WT, crc, ptsN, and crc ptsN backgrounds carrying pWW0 during growth on preferred versus non-preferred carbon sources.
Hypothesis: Global catabolite repression acts both upstream and downstream of XylR.
Type: genetic perturbation
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