U.S. flag

An official website of the United States government

Format

Send to:

Choose Destination

topA DNA topoisomerase I [ Escherichia coli str. K-12 substr. MG1655 ]

Gene ID: 945862, updated on 17-Jul-2025
Official Symbol
topA
Official Full Name
DNA topoisomerase I
Primary source
ECOCYC:EG11013
Locus tag
b1274
See related
ASAP:ABE-0004275
Gene type
protein coding
RefSeq status
REVIEWED
Organism
Escherichia coli str. K-12 substr. MG1655 (strain: K-12, substrain: MG1655)
Lineage
Bacteria; Pseudomonadati; Pseudomonadota; Gammaproteobacteria; Enterobacterales; Enterobacteriaceae; Escherichia
Also known as
ECK1268; supX
Summary
Topoisomerase I is a type IA topoisomerase which is responsible for relaxing negative supercoils in DNA. [More information is available at EcoCyc: EG11013].
NEW
Try the new Gene table
Try the new Transcript table
Sequence:
NC_000913.3 (1331048..1333645)

NC_000913.3Genomic Context describing neighboring genes Neighboring gene S49 peptidase family protein Neighboring gene protein YciN Neighboring gene DNA-binding transcriptional dual regulator CysB Neighboring gene uncharacterized protein YmiA

Genomic Sequence:
NC_000913.3

Go to nucleotide: Graphics FASTA GenBank

Related articles in PubMed

  1. Protein-nucleotide interactions in E. coli DNA topoisomerase I. Feinberg H, et al. Nat Struct Biol, 1999 Oct. PMID 10504732
  2. Crystallization of a 67 kDa fragment of Escherichia coli DNA topoisomerase I. Lima CD, et al. J Mol Biol, 1993 Aug 20. PMID 8396651
  3. Effect of the deletion of the sigma 32-dependent promoter (P1) of the Escherichia coli topoisomerase I gene on thermotolerance. Qi H, et al. Mol Microbiol, 1996 Aug. PMID 8878034
  4. Regulation of Escherichia coli topA gene transcription: involvement of a sigmaS-dependent promoter. Qi H, et al. J Mol Biol, 1997 Apr 4. PMID 9126832
  5. DNA supercoiling and bacterial adaptation: thermotolerance and thermoresistance. Tse-Dinh YC, et al. Trends Microbiol, 1997 Aug. PMID 9263411

See all (120) citations in PubMed

GeneRIFs: Gene References Into Functions

What's a GeneRIF?
  1. Topoisomerase I Essentiality, DnaA-Independent Chromosomal Replication, and Transcription-Replication Conflict in Escherichia coli.
    Title: Topoisomerase I Essentiality, DnaA-Independent Chromosomal Replication, and Transcription-Replication Conflict in Escherichia coli.
  2. Supercoiling, R-loops, Replication and the Functions of Bacterial Type 1A Topoisomerases.
    Title: Supercoiling, R-loops, Replication and the Functions of Bacterial Type 1A Topoisomerases.
  3. we observe that a single residue substitution (R168C) results in a high rate of head-to-tail (tandem) short sequence duplications, which are independent of existing sequence repeats. Finally, we show that the unique mutation spectrum of topA mutants enhances the emergence of antibiotic resistance in comparison to mismatch-repair (mutS) mutators, and leads to new resistance genotypes.
    Title: Point mutations in topoisomerase I alter the mutation spectrum in E. coli and impact the emergence of drug resistance genotypes.
  4. Study finding that both E. coli topo I and III control R-loop formation/accumulation, mostly to inhibit unregulated replication, may suggest that R-loops have been a problem early in the evolution of life. Furthermore, data show that E. coli cells can survive in the absence of type 1A topos, owing to the surproduction of topo IV that can relax excess negative supercoiling and prevent R-loop formation.
    Title: Topoisomerases I and III inhibit R-loop formation to prevent unregulated replication in the chromosomal Ter region of Escherichia coli.
  5. the CyaA(N600Y) mutant has a transcriptome indicative of increased CRP activity, pointing to an unknown role for CyaA and / or cAMP in gene expression..We show that the large scale transcriptomic changes in the topoisomerase I (FusA(A608E)-TopA(S180L)) mutant likely result from increased negative supercoiling in the cell.
    Title: Modulation of Global Transcriptional Regulatory Networks as a Strategy for Increasing Kanamycin Resistance of the Translational Elongation Factor-G Mutants in Escherichia coli.
  6. Escherichia coli RecA physically interacts with topoisomerase I to modulate the chromosomal DNA supercoiling.
    Title: Investigating direct interaction between Escherichia coli topoisomerase I and RecA.
  7. Structural study shows how the C-terminal domains of E. coli topoisomerase I bind single-stranded DNA to recognize the accumulation of negative supercoils in duplex DNA.
    Title: Structural basis for suppression of hypernegative DNA supercoiling by E. coli topoisomerase I.
  8. Antimicrobial susceptibility and SOS-dependent increase in mutation frequency are impacted by Escherichia coli topoisomerase I C-terminal point mutation.
    Title: Antimicrobial Susceptibility and SOS-Dependent Increase in Mutation Frequency Are Impacted by Escherichia coli Topoisomerase I C-Terminal Point Mutation.
  9. Data indicate that transcription-coupled DNA supercoiling (TCDS) in topoisomerase I deficient (topA) is dependent on promoter strength.
    Title: Dependence of transcription-coupled DNA supercoiling on promoter strength in Escherichia coli topoisomerase I deficient strains.
  10. Topoisomerase I relaxes DNA in slow processive runs but with short pauses before runs.
    Title: Bacterial topoisomerase I and topoisomerase III relax supercoiled DNA via distinct pathways.
Submit: New GeneRIF Correction See all GeneRIFs (19)
Products Interactant Other Gene Complex Source Pubs Description

Homology

Gene Ontology Provided by EcoCyc

Function Evidence Code Pubs
enables DNA topoisomerase activity IMP
Inferred from Mutant Phenotype
more info
 PubMed 
enables DNA topoisomerase type I (single strand cut, ATP-independent) activity IBA
Inferred from Biological aspect of Ancestor
more info
  
enables DNA topoisomerase type I (single strand cut, ATP-independent) activity IMP
Inferred from Mutant Phenotype
more info
 PubMed 
enables RNA topoisomerase activity IDA
Inferred from Direct Assay
more info
 PubMed 
enables protein binding IPI
Inferred from Physical Interaction
more info
 PubMed 
enables zinc ion binding IEA
Inferred from Electronic Annotation
more info
  
Process Evidence Code Pubs
involved_in DNA topological change IBA
Inferred from Biological aspect of Ancestor
more info
  
acts_upstream_of_or_within DNA topological change IGI
Inferred from Genetic Interaction
more info
 PubMed 
involved_in chromosome segregation IBA
Inferred from Biological aspect of Ancestor
more info
  
Component Evidence Code Pubs
located_in cytosol IDA
Inferred from Direct Assay
more info
 PubMed 
Preferred Names
DNA topoisomerase I
NP_415790.1

NEW Try the new Transcript table

Genome Annotation

The following sections contain reference sequences that belong to a specific genome build. Explain

Reference assembly

Genomic

  1. NC_000913.3 Reference assembly

    Range
    1331048..1333645
    Download
    GenBank, FASTA, Sequence Viewer (Graphics)

mRNA and Protein(s)

  1. NP_415790.1 DNA topoisomerase I

    See identical proteins and their annotated locations for NP_415790.1

    Status: REVIEWED

    UniProtKB/TrEMBL
    A0A8S7BEL4
    Conserved Domains (1) summary
    PRK07561
    Location:2 → 849
    PRK07561; DNA topoisomerase I subunit omega; Validated
Nucleotide Protein
Heading Accession and Version

Gene LinkOut

The following LinkOut resources are supplied by external providers. These providers are responsible for maintaining the links.