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Protein

Sensor protein PhoQ

Gene

phoQ

Organism
Escherichia coli (strain K12)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Member of the two-component regulatory system PhoP/PhoQ involved in adaptation to low Mg2+ environments and the control of acid resistance genes. In low periplasmic Mg2+, PhoQ functions as a membrane-associated protein kinase that undergoes autophosphorylation and subsequently transfers the phosphate to PhoP, resulting in the expression of PhoP-activated genes (PAG) and repression of PhoP-repressed genes (PRG). In high periplasmic Mg2+, acts as a protein phosphatase that dephosphorylates phospho-PhoP, resulting in the repression of PAG and may lead to expression of some PRG (By similarity). PhoP-regulated transcription is redox-sensitive, being activated when the periplasm becomes more reducing (deletion of dsbA/dsbB, or treatment with dithiothreitol). MgrB acts between DsbA/DsbB and PhoP/PhoQ in this pathway; the 2 periplasmic Cys residues of MgrB are required for its action on PhoQ, which then acts on PhoP. Mediates magnesium influx to the cytosol by activation of mgtA. Promotes expression of the two-component regulatory system rstA/rstB and transcription of the hemL, mgrB, nagA, slyB, vboR and yrbL genes.By similarity1 Publication

Catalytic activityi

ATP + protein L-histidine = ADP + protein N-phospho-L-histidine.

Enzyme regulationi

Acetyl-CoA acts as a non-competitive inhibitor of the PhoQ autokinase activity. Feedback inhibited by MgrB, which seems to bind PhoQ, altering its activity and that of downstream effector PhoP.3 Publications

Kineticsi

  1. KM=20.93 µM for ATP (at 22 degrees Celsius and pH 8, in the presence of 50 mM KCl and 1 mM MgCl2)2 Publications
  2. KM=55 µM for ATP (at 22 degrees Celsius and pH 8, in the presence of 25 mM KCl and 0.4 mM MgCl2)2 Publications

    Sites

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Metal bindingi151Divalent metal cation1
    Metal bindingi152Divalent metal cation1
    Sitei202Plays a critical role in the switching between kinase and phosphatase states1
    Metal bindingi385Magnesium1
    Metal bindingi442Magnesium1

    Regions

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Nucleotide bindingi385 – 393ATP9
    Nucleotide bindingi415 – 420ATP6
    Nucleotide bindingi434 – 446ATPAdd BLAST13

    GO - Molecular functioni

    • ATP binding Source: UniProtKB-KW
    • metal ion binding Source: EcoCyc
    • phosphoprotein phosphatase activity Source: UniProtKB-KW
    • phosphorelay sensor kinase activity Source: EcoCyc

    GO - Biological processi

    • cellular response to magnesium starvation Source: EcoCyc
    • phosphorelay signal transduction system Source: EcoCyc
    • protein autophosphorylation Source: EcoCyc
    Complete GO annotation...

    Keywords - Molecular functioni

    Hydrolase, Kinase, Protein phosphatase, Transferase

    Keywords - Biological processi

    Two-component regulatory system

    Keywords - Ligandi

    ATP-binding, Magnesium, Metal-binding, Nucleotide-binding

    Enzyme and pathway databases

    BioCyciEcoCyc:PHOQ-MONOMER.
    ECOL316407:JW1115-MONOMER.
    BRENDAi2.7.13.3. 2026.

    Names & Taxonomyi

    Protein namesi
    Recommended name:
    Sensor protein PhoQ (EC:2.7.13.3, EC:3.1.3.-)
    Alternative name(s):
    Sensor histidine protein kinase/phosphatase PhoQ
    Gene namesi
    Name:phoQ
    Ordered Locus Names:b1129, JW1115
    OrganismiEscherichia coli (strain K12)
    Taxonomic identifieri83333 [NCBI]
    Taxonomic lineageiBacteriaProteobacteriaGammaproteobacteriaEnterobacteralesEnterobacteriaceaeEscherichia
    Proteomesi
    • UP000000318 Componenti: Chromosome
    • UP000000625 Componenti: Chromosome

    Organism-specific databases

    EcoGeneiEG10732. phoQ.

    Subcellular locationi

    Topology

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Topological domaini1 – 16CytoplasmicSequence analysisAdd BLAST16
    Transmembranei17 – 37HelicalSequence analysisAdd BLAST21
    Topological domaini38 – 194PeriplasmicSequence analysisAdd BLAST157
    Transmembranei195 – 215HelicalSequence analysisAdd BLAST21
    Topological domaini216 – 486CytoplasmicSequence analysisAdd BLAST271

    GO - Cellular componenti

    • integral component of membrane Source: UniProtKB-KW
    • intracellular Source: GOC
    • plasma membrane Source: EcoCyc
    Complete GO annotation...

    Keywords - Cellular componenti

    Cell inner membrane, Cell membrane, Membrane

    Pathology & Biotechi

    Mutagenesis

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Mutagenesisi27V → N: Shows Mg(2+)-dependent signaling and partial gene activation activity; when associated with A-202. 1 Publication1
    Mutagenesisi30L → N: Shows Mg(2+)-dependent signaling and displays higher gene activation activity than wild-type; when associated with A-202. 1 Publication1
    Mutagenesisi47T → L: No significant effect (with or without MgCl(2) or CaCl(2)). 1 Publication1
    Mutagenesisi48T → A, C, E, M, N, Q, S or V: No significant effect (with or without MgCl(2) or CaCl(2)). 1 Publication1
    Mutagenesisi48T → D, G, H, I, K, L, P or R: Confers less than 30% of the wild-type levels of PhoP/PhoQ-signaling cascade in absence of CaCl(2) or MgCl(2). 1 Publication1
    Mutagenesisi48T → F or W: Decreased sensitivity to repression by calcium but not by magnesium. 1 Publication1
    Mutagenesisi48T → Y: Higher activity than wild-type (with or without MgCl(2) or CaCl(2)). 1 Publication1
    Mutagenesisi50R → D: Large decrease in the transcriptional activation of PhoQ-dependent genes. 1 Publication1
    Mutagenesisi54G → D: Very large decrease in the transcriptional activation of PhoQ-dependent genes. 1 Publication1
    Mutagenesisi68N → L: No significant effect (with or without MgCl(2) or CaCl(2)). 1 Publication1
    Mutagenesisi90D → A: No significant effect (with or without MgCl(2) or CaCl(2)). 1 Publication1
    Mutagenesisi148 – 154EDDDDAE → QNNNNAQ: Unable to bind divalent cations in vitro and impaired in the ability to respond to Mg(2+) deprivation in vivo. 1 Publication7
    Mutagenesisi149D → A: Wild-type effect concerning mgrB transcription. 1 Publication1
    Mutagenesisi150D → I: Wild-type effect concerning mgrB transcription. 1 Publication1
    Mutagenesisi151D → I: Wild-type effect concerning mgrB transcription. 1 Publication1
    Mutagenesisi152D → F: Wild-type effect concerning mgrB transcription. 1 Publication1
    Mutagenesisi179D → L or A: Locked-on mutant defective in Mg(2+)-sensing and unable to control its phosphorylation state and phosphotransfer to phoP. 2 Publications1
    Mutagenesisi179D → R: Very large decrease in the transcriptional activation of PhoQ-dependent genes. 2 Publications1
    Mutagenesisi199L → N: Shows Mg(2+)-dependent signaling and partial gene activation activity; when associated with A-202. 1 Publication1
    Mutagenesisi202N → A: Is blind to signal, fails to activate transcription of PhoQ-dependent genes, and abrogates transcription when coexpressed with wild-type PhoQ. Shows no detectable autophosphorylation. Still displays phosphatase activity. Recovers Mg(2+)-dependent signaling and partial gene activation activity; when associated with N-27 or N-199 or N-203 or N-205. Recovers Mg(2+)-dependent signaling and displays higher gene activation activity than wild-type; when associated with N-30. 1 Publication1
    Mutagenesisi202N → I, L, M, F, W, Y, V, C, G or P: Is blind to signal, fails to activate transcription of PhoQ-dependent genes, and abrogates transcription when coexpressed with wild-type PhoQ. 1 Publication1
    Mutagenesisi202N → R, D, Q, E or H: Shows similar activity profile to wild-type. 1 Publication1
    Mutagenesisi203L → N: Shows Mg(2+)-dependent signaling and partial gene activation activity; when associated with A-202. 1 Publication1
    Mutagenesisi205L → N: Shows Mg(2+)-dependent signaling and partial gene activation activity; when associated with A-202. 1 Publication1
    Mutagenesisi392K → A: 44-fold decrease in ATP affinity and 6-fold decrease in activity. 1 Publication1
    Mutagenesisi434R → A: 2-fold decrease in ATP affinity and 51-fold decrease in activity. 1 Publication1
    Mutagenesisi439R → A: 3-fold decrease in ATP affinity and 2-fold increase in activity. 1 Publication1

    PTM / Processingi

    Molecule processing

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    ChainiPRO_00000748371 – 486Sensor protein PhoQAdd BLAST486

    Amino acid modifications

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Modified residuei277Phosphohistidine; by autocatalysisPROSITE-ProRule annotation1

    Keywords - PTMi

    Phosphoprotein

    Proteomic databases

    PaxDbiP23837.
    PRIDEiP23837.

    Expressioni

    Inductioni

    The phoP/phoQ operon is positively autoregulated by both PhoP and PhoQ in a Mg2+-dependent manner, inhibited at high Mg2+ concentrations (PubMed:10464230). Induced by dsbA disruption and dithiothreitol (PubMed:22267510).2 Publications

    Interactioni

    Subunit structurei

    Homodimer; probably dimerizes via the cytoplasmic domain (Probable). Probably interacts with MgrB in the periplasm, altering its activity and that of downstream effector PhoP.Curated3 Publications

    Protein-protein interaction databases

    DIPiDIP-10501N.
    IntActiP23837. 1 interactor.
    STRINGi511145.b1129.

    Structurei

    Secondary structure

    1486
    Legend: HelixTurnBeta strandPDB Structure known for this area
    Show more details
    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Helixi46 – 62Combined sources17
    Beta strandi64 – 66Combined sources3
    Beta strandi69 – 71Combined sources3
    Helixi76 – 79Combined sources4
    Beta strandi85 – 89Combined sources5
    Beta strandi95 – 100Combined sources6
    Helixi103 – 108Combined sources6
    Helixi111 – 113Combined sources3
    Beta strandi114 – 116Combined sources3
    Beta strandi118 – 125Combined sources8
    Helixi126 – 133Combined sources8
    Helixi137 – 148Combined sources12
    Beta strandi154 – 164Combined sources11
    Beta strandi168 – 170Combined sources3
    Beta strandi173 – 178Combined sources6
    Helixi183 – 185Combined sources3
    Beta strandi337 – 339Combined sources3
    Helixi340 – 354Combined sources15
    Turni355 – 358Combined sources4
    Beta strandi361 – 365Combined sources5
    Beta strandi371 – 374Combined sources4
    Helixi376 – 393Combined sources18
    Beta strandi395 – 404Combined sources10
    Beta strandi409 – 418Combined sources10
    Helixi422 – 424Combined sources3
    Helixi427 – 429Combined sources3
    Helixi446 – 455Combined sources10
    Beta strandi459 – 464Combined sources6
    Beta strandi468 – 476Combined sources9

    3D structure databases

    Select the link destinations:
    PDBei
    RCSB PDBi
    PDBji
    Links Updated
    PDB entryMethodResolution (Å)ChainPositionsPDBsum
    1ID0X-ray1.60A335-486[»]
    3BQ8X-ray2.50A/B43-190[»]
    3BQAX-ray2.00A/B43-190[»]
    ProteinModelPortaliP23837.
    SMRiP23837.
    ModBaseiSearch...
    MobiDBiSearch...

    Miscellaneous databases

    EvolutionaryTraceiP23837.

    Family & Domainsi

    Domains and Repeats

    Feature keyPosition(s)DescriptionActionsGraphical viewLength
    Domaini215 – 266HAMPPROSITE-ProRule annotationAdd BLAST52
    Domaini274 – 480Histidine kinasePROSITE-ProRule annotationAdd BLAST207

    Sequence similaritiesi

    Contains 1 HAMP domain.PROSITE-ProRule annotation
    Contains 1 histidine kinase domain.PROSITE-ProRule annotation

    Keywords - Domaini

    Transmembrane, Transmembrane helix

    Phylogenomic databases

    eggNOGiENOG4105IFJ. Bacteria.
    COG0642. LUCA.
    HOGENOMiHOG000274481.
    InParanoidiP23837.
    KOiK07637.
    OMAiTLVFIYD.
    PhylomeDBiP23837.

    Family and domain databases

    Gene3Di3.30.565.10. 1 hit.
    InterProiIPR003660. HAMP_dom.
    IPR003594. HATPase_C.
    IPR005467. His_kinase_dom.
    IPR003661. HisK_dim/P.
    IPR015014. PhoQ_Sensor.
    IPR004358. Sig_transdc_His_kin-like_C.
    [Graphical view]
    PfamiPF00672. HAMP. 1 hit.
    PF02518. HATPase_c. 1 hit.
    PF08918. PhoQ_Sensor. 1 hit.
    [Graphical view]
    PRINTSiPR00344. BCTRLSENSOR.
    SMARTiSM00387. HATPase_c. 1 hit.
    [Graphical view]
    SUPFAMiSSF47384. SSF47384. 1 hit.
    SSF55874. SSF55874. 1 hit.
    PROSITEiPS50885. HAMP. 1 hit.
    PS50109. HIS_KIN. 1 hit.
    [Graphical view]

    Sequencei

    Sequence statusi: Complete.

    P23837-1 [UniParc]FASTAAdd to basket

    « Hide

            10         20         30         40         50
    MKKLLRLFFP LSLRVRFLLA TAAVVLVLSL AYGMVALIGY SVSFDKTTFR
    60 70 80 90 100
    LLRGESNLFY TLAKWENNKL HVELPENIDK QSPTMTLIYD ENGQLLWAQR
    110 120 130 140 150
    DVPWLMKMIQ PDWLKSNGFH EIEADVNDTS LLLSGDHSIQ QQLQEVREDD
    160 170 180 190 200
    DDAEMTHSVA VNVYPATSRM PKLTIVVVDT IPVELKSSYM VWSWFIYVLS
    210 220 230 240 250
    ANLLLVIPLL WVAAWWSLRP IEALAKEVRE LEEHNRELLN PATTRELTSL
    260 270 280 290 300
    VRNLNRLLKS ERERYDKYRT TLTDLTHSLK TPLAVLQSTL RSLRSEKMSV
    310 320 330 340 350
    SDAEPVMLEQ ISRISQQIGY YLHRASMRGG TLLSRELHPV APLLDNLTSA
    360 370 380 390 400
    LNKVYQRKGV NISLDISPEI SFVGEQNDFV EVMGNVLDNA CKYCLEFVEI
    410 420 430 440 450
    SARQTDEHLY IVVEDDGPGI PLSKREVIFD RGQRVDTLRP GQGVGLAVAR
    460 470 480
    EITEQYEGKI VAGESMLGGA RMEVIFGRQH SAPKDE
    Length:486
    Mass (Da):55,300
    Last modified:November 1, 1991 - v1
    Checksum:i89C6D97A3C9B8809
    GO

    Sequence databases

    Select the link destinations:
    EMBLi
    GenBanki
    DDBJi
    Links Updated
    D90393 Genomic DNA. Translation: BAA14391.1.
    U00096 Genomic DNA. Translation: AAC74213.1.
    AP009048 Genomic DNA. Translation: BAA35951.1.
    M81433 Genomic DNA. No translation available.
    PIRiB41966.
    RefSeqiNP_415647.1. NC_000913.3.
    WP_000735412.1. NZ_LN832404.1.

    Genome annotation databases

    EnsemblBacteriaiAAC74213; AAC74213; b1129.
    BAA35951; BAA35951; BAA35951.
    GeneIDi946326.
    KEGGiecj:JW1115.
    eco:b1129.
    PATRICi32117507. VBIEscCol129921_1176.

    Cross-referencesi

    Sequence databases

    Select the link destinations:
    EMBLi
    GenBanki
    DDBJi
    Links Updated
    D90393 Genomic DNA. Translation: BAA14391.1.
    U00096 Genomic DNA. Translation: AAC74213.1.
    AP009048 Genomic DNA. Translation: BAA35951.1.
    M81433 Genomic DNA. No translation available.
    PIRiB41966.
    RefSeqiNP_415647.1. NC_000913.3.
    WP_000735412.1. NZ_LN832404.1.

    3D structure databases

    Select the link destinations:
    PDBei
    RCSB PDBi
    PDBji
    Links Updated
    PDB entryMethodResolution (Å)ChainPositionsPDBsum
    1ID0X-ray1.60A335-486[»]
    3BQ8X-ray2.50A/B43-190[»]
    3BQAX-ray2.00A/B43-190[»]
    ProteinModelPortaliP23837.
    SMRiP23837.
    ModBaseiSearch...
    MobiDBiSearch...

    Protein-protein interaction databases

    DIPiDIP-10501N.
    IntActiP23837. 1 interactor.
    STRINGi511145.b1129.

    Proteomic databases

    PaxDbiP23837.
    PRIDEiP23837.

    Protocols and materials databases

    Structural Biology KnowledgebaseSearch...

    Genome annotation databases

    EnsemblBacteriaiAAC74213; AAC74213; b1129.
    BAA35951; BAA35951; BAA35951.
    GeneIDi946326.
    KEGGiecj:JW1115.
    eco:b1129.
    PATRICi32117507. VBIEscCol129921_1176.

    Organism-specific databases

    EchoBASEiEB0725.
    EcoGeneiEG10732. phoQ.

    Phylogenomic databases

    eggNOGiENOG4105IFJ. Bacteria.
    COG0642. LUCA.
    HOGENOMiHOG000274481.
    InParanoidiP23837.
    KOiK07637.
    OMAiTLVFIYD.
    PhylomeDBiP23837.

    Enzyme and pathway databases

    BioCyciEcoCyc:PHOQ-MONOMER.
    ECOL316407:JW1115-MONOMER.
    BRENDAi2.7.13.3. 2026.

    Miscellaneous databases

    EvolutionaryTraceiP23837.
    PROiP23837.

    Family and domain databases

    Gene3Di3.30.565.10. 1 hit.
    InterProiIPR003660. HAMP_dom.
    IPR003594. HATPase_C.
    IPR005467. His_kinase_dom.
    IPR003661. HisK_dim/P.
    IPR015014. PhoQ_Sensor.
    IPR004358. Sig_transdc_His_kin-like_C.
    [Graphical view]
    PfamiPF00672. HAMP. 1 hit.
    PF02518. HATPase_c. 1 hit.
    PF08918. PhoQ_Sensor. 1 hit.
    [Graphical view]
    PRINTSiPR00344. BCTRLSENSOR.
    SMARTiSM00387. HATPase_c. 1 hit.
    [Graphical view]
    SUPFAMiSSF47384. SSF47384. 1 hit.
    SSF55874. SSF55874. 1 hit.
    PROSITEiPS50885. HAMP. 1 hit.
    PS50109. HIS_KIN. 1 hit.
    [Graphical view]
    ProtoNetiSearch...

    Entry informationi

    Entry nameiPHOQ_ECOLI
    AccessioniPrimary (citable) accession number: P23837
    Entry historyi
    Integrated into UniProtKB/Swiss-Prot: November 1, 1991
    Last sequence update: November 1, 1991
    Last modified: November 2, 2016
    This is version 169 of the entry and version 1 of the sequence. [Complete history]
    Entry statusiReviewed (UniProtKB/Swiss-Prot)
    Annotation programProkaryotic Protein Annotation Program

    Miscellaneousi

    Miscellaneous

    There is a close linkage between the PhoP/PhoQ and Rcs signaling systems, and both signaling systems respond to certain external divalent cations (zinc and magnesium).
    Two-component regulatory system EvgA/EvgS interacts with PhoP/PhoQ via signal transduction mediated by phospho-EvgA.

    Keywords - Technical termi

    3D-structure, Complete proteome, Direct protein sequencing, Reference proteome

    Documents

    1. Escherichia coli
      Escherichia coli (strain K12): entries and cross-references to EcoGene
    2. PDB cross-references
      Index of Protein Data Bank (PDB) cross-references
    3. SIMILARITY comments
      Index of protein domains and families

    Similar proteinsi

    Links to similar proteins from the UniProt Reference Clusters (UniRef) at 100%, 90% and 50% sequence identity:
    100%UniRef100 combines identical sequences and sub-fragments with 11 or more residues from any organism into one UniRef entry.
    90%UniRef90 is built by clustering UniRef100 sequences that have at least 90% sequence identity to, and 80% overlap with, the longest sequence (a.k.a seed sequence).
    50%UniRef50 is built by clustering UniRef90 seed sequences that have at least 50% sequence identity to, and 80% overlap with, the longest sequence in the cluster.