CDC50A

CDC50A (PF3D7_0719500) is a P4-ATPase co-factor that operates in the transmission stages of the malaria parasite, where it binds and stabilizes the P4-ATPase-like domain of guanylate cyclase β (GCβ) during ookinete development in Plasmodium yoelii (PMID:30146157). The resulting GCβ/CDC50A complex is polarized to the ookinete extrados site of the plasma membrane by the inner membrane complex protein ISP1, and this spatial anchoring is required to initiate cGMP-dependent ookinete gliding motility (PMID:30146157). CDC50A's role is stage-restricted: in Plasmodium falciparum asexual blood stages it is not detectably expressed and does not partner GCα, with CDC50B and CDC50C instead filling the blood-stage CDC50 role (PMID:35862778). A distinct P4-ATPase association is seen in vitro, where recombinant Plasmodium chabaudi ATP2 co-purifies with CDC50A (PMID:33372863). Beyond these findings, the biochemical activity of CDC50A-containing complexes has not been directly characterized in the available corpus.

1. 2018 Medium

   Established that CDC50A serves as the co-factor that binds and stabilizes the P4-ATPase-like domain of guanylate cyclase β, linking a CDC50 protein to cGMP signaling machinery rather than to a standalone lipid flippase.

   Evidence Real-time imaging and co-factor binding assay with genetic dissection of GCβ domains in Plasmodium yoelii ookinetes

   PMID:30146157

   Open questions at the time

   • Binding assay details available only from abstract
   • Whether CDC50A contributes catalytic or purely structural stabilization is not resolved
   • No structural model of the GCβ/CDC50A interface
2. 2018 Medium

   Showed how the GCβ/CDC50A complex is spatially deployed, identifying ISP1-dependent anchoring at the ookinete extrados site as the trigger for initiating gliding motility.

   Evidence Live fluorescence imaging of GCβ translocation and genetic screening of inner membrane complex proteins in Plasmodium yoelii

   PMID:30146157

   Open questions at the time

   • Molecular basis of the ISP1–complex interaction unknown
   • Whether CDC50A itself contacts ISP1 or only through GCβ is not defined
3. 2021 Low

   Tested whether CDC50A can partner a canonical P4-ATPase, showing recombinant P. chabaudi ATP2 associates with CDC50A in vitro, though catalytic activity was demonstrated only for the CDC50B-containing complex.

   Evidence Recombinant protein production, co-purification, and in vitro ATPase assay in Plasmodium chabaudi proteins

   PMID:33372863

   Open questions at the time

   • ATPase/flippase activity of the ATP2/CDC50A complex was not measured
   • In vitro association may not reflect an in vivo partnership
   • Physiological relevance of the ATP2–CDC50A pairing unestablished
4. 2022 Medium

   Defined the stage-specificity of CDC50A by showing it is not expressed in P. falciparum asexual blood stages and is not the GCα partner there, distinguishing its role from the blood-stage co-factors CDC50B and CDC50C.

   Evidence Gene tagging and conditional gene disruption in P. falciparum blood stages

   PMID:35862778

   Open questions at the time

   • Does not address CDC50A function in P. falciparum transmission stages
   • Negative expression result does not rule out low-level or conditional expression

• The intrinsic biochemical activity of any CDC50A-containing complex and its precise contribution (structural vs catalytic) to GCβ function remain undefined.
• No direct measurement of activity for a CDC50A-containing complex
• No structural characterization of CDC50A
• Function in P. falciparum sexual/mosquito stages uncharacterized