Q46864 · MQSA_ECOLI

Function

function

Antitoxin component of a type II toxin-antitoxin (TA) system. Labile antitoxin that binds to the MqsR mRNA interferase toxin and neutralizes its endoribonuclease activity. Overexpression prevents MqsR-mediated cessation of cell growth and inhibition of cell proliferation. Initially reported to act as a cotranscription factor with MqsA (PubMed:19690171, PubMed:20105222).
Following further experiments, the MqsR-MqsA complex does not bind DNA and all reported data are actually due to a small fraction of free MqsA alone binding DNA. Addition of MqsR to a preformed MqsA-promoter DNA complex causes dissociation of the MqsA-DNA complex, probably causing derepression of MqsA-repressed transcripts (PubMed:23172222).
MqsA binds to 2 palindromes in the promoter region of the mqsRA operon activating its transcription. Binds to other promoters, inducing mcbR and spy and repressing cspD among others (PubMed:20105222).
Binds to and represses the rpoS promoter, the master stress regulator, resulting in decreased cyclic-di-GMP, reduced stress resistance, increased cell motility and decreased biofilm formation; in these experiments 5 TA systems are missing (lacks MazEF, RelEB, ChpB, YoeB-YefM, YafQ-DinJ) (PubMed:21516113).
An earlier study showed overexpression alone increases biofilm formation, perhaps by repressing cspD; in these experiments the 5 TA systems are present (PubMed:20105222).
Represses the csgD promoter. In the presence of stress, when this protein is degraded, the promoters it represses are derepressed, leading to biofilm formation (Probable). This TA system mediates cell growth during bile acid deoxycholate stress by degrading mRNA for probable deoxycholate-binding protein YgiS; bile acid detergents such as deoxycholate are important for host defense against bacterial growth in the gall bladder and duodenum (PubMed:25534751).

Cofactor

Zn2+ (UniProtKB | Rhea| CHEBI:29105 )

Note: Binds 1 Zn2+ ion per subunit.

Temperature Dependence

The MqsR-MqsA complex is exceptionally thermostable with a Tm of 83.4 degress Celsius versus 48.1 degress Celsius for MqsR and 61.1 degress Celsius for MqsA.

Features

Showing features for binding site, dna binding.

TypeIDPosition(s)Description
Binding site3Zn2+ (UniProtKB | ChEBI); structural
Binding site6Zn2+ (UniProtKB | ChEBI); structural
Binding site37Zn2+ (UniProtKB | ChEBI); structural
Binding site40Zn2+ (UniProtKB | ChEBI); structural
DNA binding85-104H-T-H motif

GO annotations

AspectTerm
Cellular Componenttoxin-antitoxin complex
Molecular Functionmetal ion binding
Molecular Functionprotein homodimerization activity
Molecular Functionsequence-specific DNA binding
Biological Processregulation of DNA-templated transcription
Biological Processsingle-species biofilm formation

Keywords

Enzyme and pathway databases

Names & Taxonomy

Protein names

  • Recommended name
    Antitoxin MqsA

Gene names

    • Name
      mqsA
    • Synonyms
      ygiT
    • Ordered locus names
      b3021, JW2989

Organism names

  • Taxonomic identifier
  • Strains
    • K12 / MG1655 / ATCC 47076
    • K12 / W3110 / ATCC 27325 / DSM 5911
  • Taxonomic lineage
    Bacteria > Pseudomonadota > Gammaproteobacteria > Enterobacterales > Enterobacteriaceae > Escherichia

Accessions

  • Primary accession
    Q46864
  • Secondary accessions
    • Q2M9H9

Proteomes

Subcellular Location

Phenotypes & Variants

Disruption phenotype

Essential for growth, it cannot be disrupted (PubMed:16768798).
A double mqsR-mqsA deletion leads to increased rpoS mRNA levels, resulting in increased cyclic-di-GMP levels, increasing stress resistance, increased biofilm formation (PubMed:21516113).
The double mutant has increased metabolism and respiration in the presence of the bile acid deoxycholate and consequently grows less well. Decreases cell survival in the presence of 20% deoxycholate (PubMed:25534751).

Features

Showing features for mutagenesis.

TypeIDPosition(s)Description
Mutagenesis61Decreases DNA-binding, decreases thermostability of MqsR-MqsA complex.
Mutagenesis9750-fold reduction in DNA-binding.
Mutagenesis97-101Abolishes DNA-binding, including binding to the rpoS promoter.
Mutagenesis10110-fold reduction in DNA-binding.

PTM/Processing

Features

Showing features for chain.

TypeIDPosition(s)Description
ChainPRO_00001497621-131Antitoxin MqsA

Post-translational modification

Degraded in the presence of oxidative stress, maybe by the Lon and/or ClpX proteases.

Proteomic databases

Expression

Induction

Induced by amino acid starvation, glucose starvation and when translation is blocked. Induction is decreased in the absence of the Lon protease suggesting, by homology to other toxin-antitoxin systems, that Lon may degrade the MqsA antitoxin. Transcription is activated by MqsA (PubMed:20105222).
It has been suggested that MqsA represses its own operon (PubMed:19690171).
Not more induced in persister cells (PubMed:16768798).
A member of the mqsRA operon. This operon induced by ectopic expression of toxins RelE, HicA and YafQ but not by MazF or HicA (PubMed:23432955).

Interaction

Subunit

Homodimer. Crystallizes as a heterotetramer with MqsA, MqsR-MqsA2-MqsR (PubMed:20041169).
Purifies as a probable heterohexamer of 2 MqsR dimers and 1 MqsA dimer (PubMed:19690171).
Binds promoter DNA as a dimer (PubMed:21068382).
When the 2 dissociate the MsqR mRNA interferase becomes active

Binary interactions

Protein-protein interaction databases

Family & Domains

Features

Showing features for domain.

TypeIDPosition(s)Description
Domain74-127HTH cro/C1-type

Domain

The Zn-binding N-terminal domain (residues 1-65) binds to the MqsR mRNA interferase toxin and makes contact with the DNA phosphate backbone, while the C-terminus (residues 70-131) binds the promoter in a sequence-specific manner. They are linked by a short flexible domain (PubMed:22789559).

Phylogenomic databases

Family and domain databases

Sequence

  • Sequence status
    Complete
  • Length
    131
  • Mass (Da)
    14,703
  • Last updated
    1996-11-01 v1
  • Checksum
    AA26A2793AD84447
MKCPVCHQGEMVSGIKDIPYTFRGRKTVLKGIHGLYCVHCEESIMNKEESDAFMAQVKAFRASVNAETVAPEFIVKVRKKLSLTQKEASEIFGGGVNAFSRYEKGNAQPHPSTIKLLRVLDKHPELLNEIR

Keywords

Sequence databases

Nucleotide SequenceProtein SequenceMolecule TypeStatus
U28377
EMBL· GenBank· DDBJ
AAA69189.1
EMBL· GenBank· DDBJ
Genomic DNA
U00096
EMBL· GenBank· DDBJ
AAC76057.1
EMBL· GenBank· DDBJ
Genomic DNA
AP009048
EMBL· GenBank· DDBJ
BAE77077.1
EMBL· GenBank· DDBJ
Genomic DNA

Genome annotation databases

Similar Proteins

Disclaimer

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