GyrA

GyrA (PF3D7_1223300) is a nuclear-encoded catalytic subunit of the P. falciparum DNA gyrase, an enzyme implicated in apicoplast DNA replication (PMID:17220464, PMID:17499371). Co-expression of GyrA functional domains with full-length PfGyrB reconstitutes typical DNA cleavage activity, placing GyrA at the catalytic core of the holoenzyme, and GyrA carries a unique leucine heptad repeat implicated in dimerization (PMID:17220464). The holoenzyme's role in apicoplast DNA maintenance is supported by the observation that novobiocin, a GyrB ATPase inhibitor, reduces the apicoplast/nuclear DNA ratio (PMID:17499371). Selective knockdown of GyrA mRNA blocks intraerythrocytic development, maturation, and replication, establishing that GyrA is essential for parasite proliferation across all intraerythrocytic stages (PMID:22474358). Beyond these findings — the demonstrated cleavage activity, apicoplast replication role, and essentiality — no further mechanistic detail on PF3D7_1223300 has been characterized in the available corpus; direct biochemical characterization of native PfGyrA has been limited by purification difficulties, and its contribution to supercoiling has been inferred from hybrid reconstitution using E. coli GyrA as a surrogate.

1. 2007 Medium

   To establish whether GyrA contributes to the catalytic activity of the parasite gyrase, its functional domains were tested for DNA cleavage in combination with GyrB, defining GyrA as part of the catalytic core and identifying a candidate dimerization element.

   Evidence Cloning and expression of GyrA functional domains, in vitro DNA cleavage assay with full-length PfGyrB, and sequence analysis identifying a leucine heptad repeat, in P. falciparum

   PMID:17220464

   Open questions at the time

   • Full-length native PfGyrA activity not demonstrated, only functional domains
   • Dimerization via the leucine heptad repeat inferred from sequence, not experimentally shown
   • Supercoiling activity not addressed
2. 2007 Medium

   To connect the gyrase to a cellular process, GyrA protein was detected in parasite lysates and the holoenzyme was linked to apicoplast DNA replication through drug perturbation.

   Evidence Western blot with anti-recombinant GyrA antibody and quantitative PCR of apicoplast/nuclear DNA ratio following novobiocin treatment, in P. falciparum

   PMID:17499371

   Open questions at the time

   • Apicoplast role inferred from novobiocin, which targets GyrB ATPase, not GyrA directly
   • Subcellular localization of GyrA not directly determined
   • No genetic evidence tying GyrA specifically to apicoplast DNA replication
3. 2012 Medium

   To test whether GyrA is required for parasite viability, its mRNA was selectively knocked down, establishing GyrA as essential across all intraerythrocytic stages.

   Evidence Peptide-morpholino oligomer conjugate-directed mRNA cleavage with in vitro cleavage assay, fluorescence microscopy of delivery, and parasite proliferation assay, in P. falciparum

   PMID:22474358

   Open questions at the time

   • Does not resolve which molecular activity of GyrA underlies essentiality
   • Off-target contributions of the knockdown reagent not fully excluded
   • No rescue experiment
4. 2021 Low

   To assess GyrA's requirement for supercoiling, a hybrid holoenzyme was reconstituted, indicating GyrA is needed for supercoiling activity but relying on an E. coli surrogate rather than native PfGyrA.

   Evidence Hybrid enzyme reconstitution combining PfGyrB with E. coli GyrA, supercoiling assay, and inhibitor screening, in P. falciparum context

   PMID:34339271

   Open questions at the time

   • GyrA contribution inferred from E. coli surrogate; native PfGyrA not purified or assayed
   • Supercoiling by an all-Plasmodium holoenzyme not demonstrated
   • Inhibitor sensitivity attributed to the GyrB partner
5. 2026 Low

   To identify GyrA active-site features for drug targeting, computational modeling nominated catalytic residues and an inhibitory mechanism for withanolides.

   Evidence Molecular docking, molecular dynamics simulation, and MM/GBSA free energy calculation (computational only), for P. falciparum GyrA

   PMID:42337902

   Open questions at the time

   • Predicted residues GLU648, LYS647, TYR590 not experimentally validated
   • Inhibitory mechanism not confirmed in vitro or in parasites
   • No demonstration of withanolide activity against native enzyme

• Direct biochemical characterization of native full-length PfGyrA — its supercoiling activity within an all-Plasmodium holoenzyme, structural basis of dimerization, and validated inhibitor-binding residues — remains unresolved in the available corpus.
• Native PfGyrA purification difficulties unresolved
• No structure of PfGyrA or the intact holoenzyme
• Functional role of the leucine heptad repeat in dimerization untested