PF3D7_1137400

PF3D7_1137400 (PfRCC-PIP) is an RCC1-motif-containing regulatory protein of Plasmodium falciparum that functions as a scaffold coordinating phosphatase and kinase activity (PMID:30429842). It directly binds P. falciparum Protein Phosphatase type-1 (PfPP1) in vitro and co-exists in complex with PfPP1 in the parasite, establishing it as a major PfPP1 partner (PMID:30429842); in a Xenopus oocyte heterologous system it interacts with endogenous PP1 and synergizes with suboptimal progesterone to drive oocyte maturation, indicating it acts as a positive regulator of PP1 activity (PMID:30429842). Its RCC1-motif region additionally engages the parasite kinase CDPK7, extending its role to that of a kinase-anchoring protein and positioning it to couple phosphorylation with dephosphorylation (PMID:30429842). Attempts to generate knockout parasites failed, consistent with an essential function (PMID:30429842). Beyond these interactions and the failed-knockout result, no further mechanistic detail — including in situ localization, substrate specificity, or cell-cycle role — has been characterized in the available corpus.

1. 2018 Medium

   Establishing that PF3D7_1137400 is a bona fide PfPP1 partner answered whether this RCC1-motif protein physically and functionally associates with the parasite's major phosphatase.

   Evidence In vitro direct interaction assay plus co-immunoprecipitation/complex detection in P. falciparum lysate

   PMID:30429842

   Open questions at the time

   • Does not define which region of PfPP1 or PfRCC-PIP mediates binding
   • No in situ demonstration of where in the parasite the complex forms
   • Stoichiometry and additional complex members unresolved
2. 2018 Medium

   A heterologous functional assay resolved whether the interaction with PP1 is merely physical or regulatory, showing PF3D7_1137400 positively modulates PP1 activity.

   Evidence Xenopus oocyte maturation assay measuring synergy with suboptimal progesterone doses via endogenous PP1

   PMID:30429842

   Open questions at the time

   • Activation demonstrated on endogenous Xenopus PP1, not directly on PfPP1 in the parasite
   • Molecular mechanism of PP1 activation not defined
   • Physiological substrates dephosphorylated under this regulation unknown
3. 2018 Low

   Identifying a kinase partner tested whether PF3D7_1137400 acts solely on the phosphatase side or bridges kinase and phosphatase activities, revealing a dual anchoring role.

   Evidence Pulldown/binding assay between the RCC1-motif region of PF3D7_1137400 and the kinase CDPK7

   PMID:30429842

   Open questions at the time

   • Single pulldown without reciprocal validation described
   • Whether CDPK7 and PfPP1 bind simultaneously or competitively is untested
   • Functional consequence of the CDPK7 interaction not measured
4. 2018 Low

   Reverse genetics addressed whether the gene is dispensable, indicating essentiality for blood-stage survival.

   Evidence Attempted gene knockout in P. falciparum yielding no viable knockout parasites

   PMID:30429842

   Open questions at the time

   • Essentiality inferred from failure to obtain KO, not from conditional depletion or complementation
   • Stage-specific requirement not defined
   • No phenotype available to link essentiality to the PP1/CDPK7 functions

• How PF3D7_1137400 integrates PfPP1 and CDPK7 activity in situ, its substrates, and its cellular localization and cell-cycle role remain unknown.
• No conditional knockdown/knockout phenotype characterized
• No substrate or localization data
• Simultaneous versus mutually exclusive binding of kinase and phosphatase untested