Bacterial DNA topoisomerase IV (Topoisomerase IV (Topo IV); sometimes DNA gyrase (for the paired target))

Molecular Classification

Enzyme, Type II DNA topoisomerase, Heterotetrameric ATPase (consisting of ParC and ParE subunits)

Other Names

Topo IV, ParC/ParE complex (gene names for subunits), DNA gyrase (when referenced as the type II bacterial topoisomerase, but more accurately a related enzyme)

Disease Roles

Infection (targeted by antibiotics against pathogenic bacteria)Other (potential role in antimicrobial resistance development)

Bacterial DNA topoisomerase IV Overview

Bacterial DNA topoisomerase IV is a type II topoisomerase enzyme found in most bacteria (distinct from eukaryotic topoisomerase II), usually composed of ParC and ParE subunits forming a heterotetramer. Its principal biological functions are unlinking replicated DNA strands (decatenation) and relaxing supercoiled DNA, essential for chromosome segregation during cell division and the maintenance of DNA topology. Topoisomerase IV works primarily behind the replication fork to untangle daughter chromosomes, while the related enzyme DNA gyrase acts ahead of the fork to remove excess positive supercoiling and introduce negative supercoils. Both enzymes are validated targets for several major antibacterial drug classes, especially fluoroquinolones and emerging novel topoisomerase inhibitors. Resistance can arise through mutations in their subunit genes, and their inhibition underpins one of the most important mechanisms for broad-spectrum antibiotic action against pathogenic bacteria.

Mechanism of Action

Enzyme inhibition: antibiotics bind and stabilize DNA-enzyme complexes, preventing re-ligation after DNA breakage. Poisoning: some drugs trap the covalent enzyme-DNA intermediate, leading to DNA damage and cell death. ATPase inhibition (for some newer agents). Dual targeting (some molecules inhibit both DNA gyrase and topoisomerase IV).

Biological Functions

Decatenation (untangling daughter chromosomes after DNA replication)

Relaxation of supercoiled DNA (especially positive supercoils)

Facilitation of chromosome segregation during cell division

Contribution to DNA topology management in replication, transcription, maintenance

Disease Associations

Infection (targeted by antibiotics against pathogenic bacteria)

Other (potential role in antimicrobial resistance development)

Safety Considerations

Target-mediated antibiotic resistance: frequent point mutations in target genes lead to decreased drug binding, therapeutic failure
Collateral bacterial DNA damage: excessive inhibition or poisoning can induce cell death or mutagenesis
Spectrum limitations: variable activity against Gram-positive and Gram-negative bacteria

Interacting Drugs

Fluoroquinolones (e.g., ciprofloxacin)

Novel bacterial topoisomerase inhibitors (NBTIs)

Gepotidacin (triazaacenaphthylene)

Zoliflodacin (spiropyrimidinetrione)

Coumarins, cyclothialidines

Simociclinones

Associated Biomarkers

Biomarker
Mutations in gyrA, gyrB, parC, or parE (can indicate resistance to fluoroquinolones and other antibacterials)
None established for patient selection/monitoring efficacy outside of resistance mutation profiling