PF3D7_0403100

PF3D7_0403100 (PfRCC-PIP) is a dual anchoring protein in Plasmodium falciparum that scaffolds phosphorylation and dephosphorylation activities. It directly binds Protein Phosphatase type-1 (PfPP1), forming a complex in the parasite where it acts as a major PfPP1 partner (PMID:30429842), and it positively regulates phosphatase activity, synergizing with suboptimal progesterone doses to promote oocyte maturation in a heterologous Xenopus assay (PMID:30429842). Its RCC1-motif-containing region additionally engages the parasite kinase PfCDPK7, identifying it as a kinase-anchoring protein alongside its phosphatase-anchoring role (PMID:30429842). Attempts to generate knock-out parasites failed, indicating the gene is essential for parasite viability (PMID:30429842). Beyond these interactions and the essentiality inference, no further mechanistic detail — including in vivo substrates, structural basis of binding, or the physiological consequences of PfCDPK7 anchoring — has been characterized in the available corpus.

1. 2018 Medium

   Whether PF3D7_0403100 physically associates with a phosphatase was unknown; establishing a direct PfPP1 interaction defined its identity as a phosphatase-binding scaffold in the parasite.

   Evidence In vitro interaction assay plus co-immunoprecipitation from parasite lysate

   PMID:30429842

   Open questions at the time

   • Binding interface / PP1-docking motif on PF3D7_0403100 not mapped
   • Endogenous substrates of the PfPP1 complex not identified
   • Stoichiometry and other complex members not defined
2. 2018 Medium

   Whether the interaction merely tethers or actively modulates PP1 was unknown; a heterologous functional assay showed PF3D7_0403100 activates PP1 to lower the progesterone threshold for oocyte maturation, establishing it as a positive regulator.

   Evidence Xenopus oocyte maturation assay with progesterone dose-response, using endogenous Xenopus PP1

   PMID:30429842

   Open questions at the time

   • Regulatory effect shown in Xenopus, not demonstrated on PfPP1 in the parasite
   • Molecular mechanism of PP1 activation unresolved
   • Single method, single lab
3. 2018 Low

   Whether PF3D7_0403100 also engages a kinase was unknown; its RCC1-motif region was shown to bind PfCDPK7, extending its role to a dual kinase- and phosphatase-anchoring scaffold.

   Evidence In vitro binding assay between the RCC1-domain fragment and PfCDPK7

   PMID:30429842

   Open questions at the time

   • Single pulldown without mutagenesis or reciprocal validation
   • Functional consequence of CDPK7 anchoring not tested
   • Interaction not confirmed in the parasite in vivo
4. 2018 Low

   Whether the gene is required for parasite survival was unknown; failure to recover knock-out clones suggested essentiality, framing PF3D7_0403100 as a candidate node in essential signaling.

   Evidence Attempted reverse-genetic gene knock-out; no viable clones recovered

   PMID:30429842

   Open questions at the time

   • Essentiality inferred from failed KO, not confirmed by conditional knockdown/knockout
   • Stage-specific requirement not established
   • No demonstration that essentiality depends on PP1 or CDPK7 binding

• The in-parasite substrates coordinated by this kinase/phosphatase scaffold and the physiological process it controls remain unknown.
• No conditional-knockdown phenotype defining the cellular process affected
• No structural or mutational mapping of the PP1- and CDPK7-binding regions
• No identification of substrates dephosphorylated/phosphorylated via the scaffold