RPS9

PF3D7_0520000 (RPS9) is a structural component of the small (40S) subunit of the P. falciparum 80S ribosome, established by high-resolution cryo-EM of the purified ribosome (PMID:24913268, PMID:26432834) and by in situ cryo-electron tomography of actively translating ribosomes inside infected erythrocytes (PMID:40825879). Its assignment to the 40S subunit holds both in ribosomes purified from blood-stage schizonts (PMID:26432834) and in the physiological translation context, where the native ribosome was resolved in eight elongation states (PMID:40825879). No experiments in the available corpus have been directed specifically at the individual function, interactions, or essentiality of RPS9 beyond its membership in the small subunit; the surrounding structural work characterizes drug binding to the small subunit (emetine at the E-site blocking translocation (PMID:24913268)) and global translation dynamics rather than RPS9 itself.

1. 2014 Medium

   Whether RPS9 is a component of the P. falciparum ribosome and where it resides was resolved by placing it structurally within the 40S small subunit of the 80S ribosome.

   Evidence Cryo-EM of the P. falciparum 80S ribosome at 3.2 A in complex with emetine

   PMID:24913268

   Open questions at the time

   • No functional experiment targeted RPS9 itself; assignment is compositional/structural only
   • No test of RPS9 essentiality or role in translation initiation/elongation
   • No interaction partners defined beyond co-membership in the small subunit
2. 2015 Medium

   Confirmation that RPS9's small-subunit assignment reflects the native blood-stage ribosome came from reconstructions of ribosomes purified from schizonts with atomic model building.

   Evidence Cryo-EM with flexible fitting and atomic model building from ribosomes purified from P. falciparum blood-stage schizonts

   PMID:26432834

   Open questions at the time

   • Independent structural confirmation but still no RPS9-directed functional assay
   • Stage-specificity of RPS9 function not addressed
   • No reciprocal validation of RPS9 contacts within the subunit
3. 2025 Medium

   Whether the small-subunit composition including RPS9 is preserved during active translation in the physiological cellular environment was addressed by resolving native translating ribosomes in situ across eight elongation states.

   Evidence In situ cryo-electron tomography of P. falciparum-infected human erythrocytes; eight high-resolution structures of native translating ribosomes

   PMID:40825879

   Open questions at the time

   • RPS9 was observed as part of the subunit but no perturbation of RPS9 was performed
   • Contribution of RPS9 to elongation-state transitions unknown
   • Drug-induced changes were interpreted at the level of the ribosome, not RPS9 specifically

• The individual function of RPS9 — its specific role in translation, its assembly requirements, its essentiality, and any non-ribosomal or moonlighting activity in P. falciparum — remains uncharacterized.
• No knockdown, knockout, or complementation data for RPS9
• No RPS9-specific interaction or crosslinking data beyond structural co-membership
• No evidence on RPS9 as an antimalarial target distinct from the ribosome as a whole