id: P06519 gene_symbol: xylR product_type: PROTEIN aliases: - 67 kDa protein status: COMPLETE taxon: id: NCBITaxon:303 label: Pseudomonas putida description: 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. alternative_records: - id: A0A1L7N7J0 relationship: REFERENCE_PROTEOME_CANDIDATE reference_proteome: UP000218731 reviewed_on: '2026-10-19' reason: Retain P06519 as the primary Swiss-Prot accession. The leading hit is a full-length xyl-upper-pathway transcriptional activator with 66.67% global identity. The source is strain mt-2 and the reference strain differs. Related regulatory function and sequence similarity do not establish the same mobile-element locus or effector specificity; retain a candidate. evidence: - type: PROTEOME_SEARCH description: MMseqs2 searched 6,919 sequences across UP000218731 at E <= 1e-5 and sensitivity 7.5, returning 24 hits. Every returned sequence was globally aligned using BLOSUM62 with gap-open -10 and extension -0.5. Scores and sequences for all 24 returned candidates are retained, with 10 detailed alignment files. The heuristic search does not establish genomic absence or unique locus identity. supported_by: - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: 'target_sequence_count: 6919' - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: 'candidate_count: 24' - type: SEQUENCE_COMPARISON description: 'A0A1L7N7J0: 380 identities across 570 global-alignment columns (66.6667% identity including gaps), 179 substitutions and 11 gap columns. Query coverage is 98.7633%; target coverage is 99.2895%. Sequence similarity is interpreted in the manual rationale. Identity over paired residues is 67.9785% (380/559); gap columns are excluded from this denominator.' supported_by: - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: |- query_length: 566 target_length: 563 alignment_columns: 570 identities: 380 mismatches: 179 gap_columns: 11 identity_percent: 66.6667 query_coverage_percent: 98.7633 target_coverage_percent: 99.2895 - type: PROTEOME_MEMBERSHIP description: The primary accession is outside every searched exact-taxon reference proteome. Current UniProt records place A0A1L7N7J0 in UP000218731 and give it the same taxon as the primary. supported_by: - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: 'primary_in_any_reference_proteome: false' - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: 'alternative_in_reference_proteome: true' - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: 'same_taxon: true' - type: RECORD_HISTORY description: 'Sampled UniSave observations: 24-JUN-2015, entry version 110.: no Proteomes cross-reference; 02-DEC-2020, entry version 124.: no Proteomes cross-reference; 27-NOV-2024, entry version 136.: no Proteomes cross-reference. These dated observations do not establish uninterrupted membership/absence, the exact change date, or UniProt''s motivation.' supported_by: - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: |- entry_date: 24-JUN-2015, entry version 110. proteomes: [] - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: |- entry_date: 02-DEC-2020, entry version 124. proteomes: [] - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: |- entry_date: 27-NOV-2024, entry version 136. proteomes: [] - type: CURATION_CONTEXT description: The primary UniProt entry records plasmid origin. Reference-proteome membership at species or strain level does not ensure coverage of every accessory plasmid. supported_by: - reference_id: file:PSEPK/xylR/xylR-record-evidence.yaml supporting_text: 'geneEncodingType: Plasmid' existing_annotations: - term: id: GO:0005524 label: ATP binding evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: 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. action: KEEP_AS_NON_CORE supported_by: - reference_id: file:PSEPK/xylR/xylR-uniprot.txt record_section: ["FT:BINDING"] supporting_text: FT BINDING 263..270 - reference_id: file:PSEPK/xylR/xylR-uniprot.txt record_section: ["FT:BINDING"] supporting_text: FT /ligand="ATP" - reference_id: PMID:9489676 supporting_text: The addition of ATP, known to trigger multimerization of the regulator at the UAS, enhanced the repression of Pr by XylR - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: use a **central AAA+ ATPase domain** to couple ATP hydrolysis to remodeling of the σ54–RNAP complex - term: id: GO:0006355 label: regulation of DNA-templated transcription evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in review: 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. action: MODIFY proposed_replacement_terms: - id: GO:0045893 label: positive regulation of DNA-templated transcription supported_by: - reference_id: PMID:2993247 supporting_text: 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. - reference_id: PMID:9489676 supporting_text: 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. - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: it is a **signal-responsive transcriptional regulator** that activates transcription of genes enabling catabolism of aromatic hydrocarbons - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: It activates the **Pu** and **Ps** promoters - term: id: GO:0043565 label: sequence-specific DNA binding evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: 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. action: ACCEPT supported_by: - reference_id: PMID:3169574 supporting_text: The C-terminal region (aa 515-558) has a putative DNA-binding structure. - reference_id: file:PSEPK/xylR/xylR-uniprot.txt record_section: ["FT:DNA_BIND"] supporting_text: FT DNA_BIND 534..553 - reference_id: PMID:9489676 supporting_text: The addition of ATP, known to trigger multimerization of the regulator at the UAS, enhanced the repression of Pr by XylR - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: 'D domain (C-terminus):** DNA binding to upstream activating sequences (UAS), typically via an HTH-type motif' - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: XylR binds UAS sites and can act at a distance, often requiring DNA looping and bending - term: id: GO:0141097 label: ligand-modulated transcription activator activity evidence_type: TAS original_reference_id: PMID:9489676 review: 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. action: NEW supported_by: - reference_id: PMID:9489676 supporting_text: 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. - reference_id: file:PSEPK/xylR/xylR-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: In the CC presence of m-xylene or m-methylbenzyl alcohol XylR activates both the - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: The N-terminal A domain is described as binding aromatic effectors and repressing the central activation domain until inducer binding - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: Deletion of the N-terminal region (e.g., removal of the A domain) yields **constitutive activity** - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: XylR then uses **ATP binding/hydrolysis**, oligomerization, and contact with **σ54-RNAP** - term: id: GO:0042203 label: toluene catabolic process evidence_type: TAS original_reference_id: PMID:2993247 review: 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. action: NEW supported_by: - reference_id: PMID:2993247 supporting_text: 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. - reference_id: PMID:16085802 supporting_text: Toluene degradation in Pseudomonas putida KT2440 pWW0 plasmid is subjected to catabolite repression. - reference_id: file:PSEPK/xylR/xylR-deep-research-openai.md supporting_text: XylR is the master regulator of the TOL plasmid *pWW0* upper pathway, which governs the initial **oxidative catabolism of toluene and xylenes** - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: it activates the **Pu promoter** driving the **upper operon** and activates σ54-class promoter **Ps1** to induce **xylS** - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: XylR is described as the principal/master regulator in the TOL plasmid network controlling degradation of **toluene and xylene isomers** - term: id: GO:0042184 label: xylene catabolic process evidence_type: TAS original_reference_id: PMID:2993247 review: 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. action: NEW supported_by: - reference_id: PMID:2993247 supporting_text: 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. - reference_id: PMID:20529863 supporting_text: 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. - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: Native effectors include **toluene and xylene isomers** references: - id: file:PSEPK/xylR/xylR-record-evidence.yaml title: Compact archived record and sequence evidence for P06519 - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms. findings: - statement: InterPro captures the sigma54 activator and DNA-binding domains of XylR but only yields broad seed annotations. - id: PMID:2993247 title: Determination of the transcription initiation site and identification of the protein product of the regulatory gene xylR for xyl operons on the TOL plasmid. findings: - statement: xylR acts positively on xyl operons for degradation of toluene and xylenes. supporting_text: 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. - statement: xylR transcription has two mapped start sites and is inducer-independent at the promoter level. supporting_text: Two initiation sites were detected which were identical in both P. putida and E. coli. The amounts of mRNA synthesized in both bacterial cells were almost the same and independent of the inducers for xyl operons. - statement: The xylR product is an approximately 67 kDa protein. supporting_text: The product of the xylR gene was identified by the maxicell system as a protein with an approximate molecular weight of 67,000. - id: PMID:3169574 title: Nucleotide sequence of the regulatory gene xylR of the TOL plasmid from Pseudomonas putida. findings: - statement: xylR encodes a 566 aa transcriptional activator for the aromatic-hydrocarbon degradative pathway. supporting_text: The 1698-bp sequence for a 566-amino acid (aa) protein (Mr 63741) was identified as the XylR-encoding sequence. - statement: The central region corresponds to the sigma-factor interaction region. supporting_text: The central region of XylR (aa 234-473) corresponds to the region that was proposed to interact with RNA polymerase having a sigma factor, NtrA - statement: The C-terminal region contains a putative DNA-binding structure. supporting_text: The C-terminal region (aa 515-558) has a putative DNA-binding structure. - id: PMID:2430049 title: Genetic, functional and sequence analysis of the xylR and xylS regulatory genes of the TOL plasmid pWW0. findings: - statement: xylR is one of the core regulatory genes of the TOL plasmid pWW0 system. supporting_text: Insertion mutations of the xylR and xylS regulatory genes of the catabolic pathway have been isolated and characterized - statement: Tn5 mutagenesis and functional analysis linked xylR to catechol 2,3-oxygenase induction. supporting_text: their ability to induce catechol 2,3-oxygenase activity determined. - id: PMID:9489676 title: Activation of the toluene-responsive regulator XylR causes a transcriptional switch between sigma54 and sigma70 promoters at the divergent Pr/Ps region of the TOL plasmid. findings: - statement: Activated XylR is a toluene-responsive regulator of the sigma54-dependent Pu and Ps promoters. supporting_text: 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. - statement: ATP promotes multimerization at the UAS and contributes to the Pr/Ps transcriptional switch. supporting_text: The addition of ATP, known to trigger multimerization of the regulator at the UAS, enhanced the repression of Pr by XylR - id: PMID:20529863 title: The Crc global regulator inhibits the Pseudomonas putida pWW0 toluene/xylene assimilation pathway by repressing the translation of regulatory and structural genes. findings: - statement: Crc represses the TOL pathway partly by binding the translation-initiation regions of xylR and xylS mRNAs. supporting_text: This study reports that Crc binds to sites located at the translation initiation regions of the mRNAs coding for XylR and XylS - statement: XylR sits within a larger catabolite-repression hierarchy rather than acting alone. supporting_text: First, Crc inhibits the translation of the XylR and XylS regulators, thereby reducing the transcription of all TOL pathway genes. - id: PMID:16085802 title: Integration of signals through Crc and PtsN in catabolite repression of Pseudomonas putida TOL plasmid pWW0. findings: - statement: The pWW0 system has been studied in a KT2440 host background. supporting_text: Toluene degradation in Pseudomonas putida KT2440 pWW0 plasmid is subjected to catabolite repression. - statement: Global regulation through Crc and PtsN modulates XylR-dependent promoter output. supporting_text: Pu and P(S1) promoters of the pWW0 TOL plasmid are down-regulated in vivo during exponential growth in rich medium. - id: file:PSEPK/xylR/xylR-uniprot.txt title: UniProt entry P06519 findings: - statement: The reviewed accession is plasmid-borne on TOL pWW0 and mapped to taxon 303 rather than the native KT2440 chromosome. - statement: UniProt records ATP-binding residues, a DNA-binding motif, and activation of xylCMABN/xylS in response to aromatic effectors. - id: file:PSEPK/xylR/xylR-deep-research-openai.md title: OpenAI deep research report for xylR findings: - statement: The deep research report converges on XylR as a sigma54-dependent aromatic-effector-responsive transcriptional activator for the TOL network. - id: file:PSEPK/xylR/xylR-deep-research-falcon.md title: Falcon (Edison Scientific) deep research report for xylR findings: - supporting_text: σ54-dependent bacterial enhancer-binding protein (bEBP) - supporting_text: it is a **signal-responsive transcriptional regulator** that activates transcription of genes enabling catabolism of aromatic hydrocarbons - supporting_text: use a **central AAA+ ATPase domain** to couple ATP hydrolysis to remodeling of the σ54–RNAP complex - supporting_text: 'D domain (C-terminus):** DNA binding to upstream activating sequences (UAS), typically via an HTH-type motif' - supporting_text: it activates the **Pu promoter** driving the **upper operon** and activates σ54-class promoter **Ps1** to induce **xylS** - supporting_text: The N-terminal A domain is described as binding aromatic effectors and repressing the central activation domain until inducer binding - supporting_text: Deletion of the N-terminal region (e.g., removal of the A domain) yields **constitutive activity** - supporting_text: XylR variants defective in activation of Ps (σ54 promoter) remained competent for repression of Pr (autoregulation) - supporting_text: 'σ54 (RpoN) is essential for Ps1 activity: Ps1 transcription is abolished in σ54-deficient backgrounds' - supporting_text: functioning as a **cytoplasmic DNA-binding transcription factor** - supporting_text: XylR also represses its own **Pr** promoter region by occupying overlapping UAS/Pr sites - id: file:PSEPK/xylR/xylR-notes.md title: xylR curation notes findings: - statement: This review treats the requested PSEPK folder as a KT2440/pWW0 context while correcting the actual curated accession to the plasmid-borne xylR protein. core_functions: - description: XylR is an aromatic-effector-responsive enhancer-binding transcription activator on TOL plasmid pWW0. In response to aromatic inducers and ATP, it multimerizes at upstream activating sequences and activates the sigma54-dependent Pu and Ps promoters, initiating expression of the upper xyl operon and xylS for toluene and xylene catabolism. molecular_function: id: GO:0141097 label: ligand-modulated transcription activator activity directly_involved_in: - id: GO:0042203 label: toluene catabolic process - id: GO:0042184 label: xylene catabolic process supported_by: - reference_id: PMID:2993247 supporting_text: 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. - reference_id: PMID:9489676 supporting_text: 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. - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: it is a **signal-responsive transcriptional regulator** that activates transcription of genes enabling catabolism of aromatic hydrocarbons - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: The N-terminal A domain is described as binding aromatic effectors and repressing the central activation domain until inducer binding - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: it activates the **Pu promoter** driving the **upper operon** and activates σ54-class promoter **Ps1** to induce **xylS** - description: XylR uses a C-terminal DNA-binding region to recognize promoter-proximal upstream activating sequences and to implement the Pr/Ps transcriptional switch that controls TOL pathway output. molecular_function: id: GO:0043565 label: sequence-specific DNA binding directly_involved_in: - id: GO:0045893 label: positive regulation of DNA-templated transcription supported_by: - reference_id: PMID:3169574 supporting_text: The C-terminal region (aa 515-558) has a putative DNA-binding structure. - reference_id: PMID:9489676 supporting_text: The addition of ATP, known to trigger multimerization of the regulator at the UAS, enhanced the repression of Pr by XylR - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: 'D domain (C-terminus):** DNA binding to upstream activating sequences (UAS), typically via an HTH-type motif' - reference_id: file:PSEPK/xylR/xylR-deep-research-falcon.md supporting_text: XylR binds UAS sites and can act at a distance, often requiring DNA looping and bending suggested_questions: - question: 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? - question: 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? suggested_experiments: - hypothesis: Aromatic effector binding and ATP-dependent multimerization jointly determine XylR promoter selectivity and output strength. description: 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. experiment_type: reporter assay - hypothesis: XylR directly occupies the known UAS elements at the divergent Pr/Ps control region in an effector-dependent manner. description: 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. experiment_type: DNA binding assay - hypothesis: Global catabolite repression acts both upstream and downstream of XylR. description: 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. experiment_type: genetic perturbation