CCT7

PF3D7_0308200 (CCT7) is a subunit of the TRiC/CCT chaperonin complex localized to the Plasmodium falciparum parasite cytosol (PMID:28067475). Regulatable knockdown of CCT7 causes a severe asexual growth defect but does not perturb protein export into the host red blood cell, indicating that the complex acts within the parasite rather than in host-cell protein trafficking (PMID:28067475). Its membership in the parasite TRiC/CCT holo-complex has been independently confirmed by affinity purification of the complex via the CCT8 subunit in P. falciparum trophozoites (PMID:36567946). In P. yoelii, the TRiC/CCT complex including CCT7 was detected in association with the CAF1/CCR4/NOT mRNA deadenylation and translational repression machinery, indicating a physical (direct or indirect) link to mRNA regulation (PMID:30703164). Beyond complex membership, the growth requirement, and this reported association, no CCT7-specific molecular mechanism, substrate, or structural detail has been characterized in the available corpus.

1. 2017 Medium

   Whether CCT7 functions within the parasite or in host-cell protein trafficking was unknown; localizing it and knocking it down established it as a cytosolic TRiC chaperonin subunit required for asexual growth but dispensable for RBC protein export.

   Evidence Epitope-tagged transgenic parasites with antibody localization plus regulatable knockdown and growth/export phenotype readouts in P. falciparum

   PMID:28067475

   Open questions at the time

   • No client/substrate proteins of the CCT7-containing complex identified
   • Mechanism linking chaperonin loss to the growth defect not defined
   • No structural characterization of CCT7 within the complex
2. 2019 Low

   Whether the parasite TRiC/CCT complex connects to mRNA regulatory machinery was untested; a Co-IP identified CCT7 among proteins associated with the CAF1/CCR4/NOT deadenylation complex, raising a possible physical link.

   Evidence GFP-tagged PyCCR4-1 co-immunoprecipitation followed by mass spectrometry (SAINT analysis) in P. yoelii schizonts

   PMID:30703164

   Open questions at the time

   • CCT7 detected only at a permissive SAINT threshold (0.1-0.35); association not independently validated
   • Direct versus indirect interaction not resolved
   • No functional follow-up specific to CCT7 in this context
3. 2022 Low

   Whether CCT7 is a bona fide member of the assembled parasite chaperonin was addressed by purifying the holo-complex through a different subunit and confirming CCT7 co-purifies.

   Evidence FLAG-tagged CCT8 affinity purification (Selection Linked Integration) with proteomics from synchronized P. falciparum trophozoites

   PMID:36567946

   Open questions at the time

   • Establishes complex membership only, with no functional characterization of CCT7
   • No stoichiometry or subunit arrangement determined
   • No substrates of the purified complex identified

• The specific molecular role of CCT7 within the TRiC/CCT complex, its folding substrates, and the functional significance of the reported CAF1/CCR4/NOT association remain unresolved.
• No CCT7-specific client proteins identified
• Functional consequence of the TRiC-CCR4/NOT association not tested for CCT7
• No structural model of CCT7 in the Plasmodium chaperonin