MRPL23

MRPL23 (PF3D7_1239100) is a mitochondrion-localized large-subunit mitoribosomal protein of Plasmodium falciparum that supports mitochondrial gene expression and electron transport chain function (PMID:36201550). Conditional knockdown reduces cytochrome bc1 complex activity and sensitizes parasites to the bc1 inhibitors atovaquone and ELQ-300, linking MRPL23 function to maintenance of mitochondrial respiratory activity (PMID:36201550). MRPL23 plays a non-redundant role in mitoribosome assembly distinct from the assembly factor RSM22: early knockdown of MRPL23 upregulates mitochondrial rRNAs and several mitoribosomal proteins, whereas RSM22 knockdown downregulates them (PMID:36201550). Late-stage loss of MRPL23 produces broad transcriptional defects across essential metabolic and mitochondrial pathways and culminates in parasite death, indicating an essential cellular role (PMID:36201550). Beyond these findings, no structural model, direct RNA- or protein-binding data, or defined position within the mitoribosome has been characterized for PF3D7_1239100 in the available corpus.

1. 2022 Medium

   Establishing where MRPL23 acts was the first step in assigning it a mitochondrial function rather than inferring one from its annotation.

   Evidence Direct subcellular localization in P. falciparum

   PMID:36201550

   Open questions at the time

   • Localization method details not fully specified and from a single study/lab
   • Sub-mitochondrial position (matrix vs. membrane-associated mitoribosome) not resolved
   • No demonstration of physical incorporation into an assembled mitoribosome
2. 2022 Medium

   Linking MRPL23 to a measurable respiratory output showed its mitochondrial role has functional consequences for electron transport.

   Evidence Conditional knockdown with cytochrome bc1 activity assay and atovaquone/ELQ-300 drug sensitivity

   PMID:36201550

   Open questions at the time

   • Whether reduced bc1 activity is direct or a downstream consequence of impaired mitochondrial translation is not distinguished
   • No identification of the specific mitochondrially encoded bc1 subunits affected
   • Single lab, single study
3. 2022 Medium

   Contrasting MRPL23 knockdown against RSM22 knockdown separated its role in mitoribosome biogenesis from that of a dedicated assembly factor.

   Evidence Conditional knockdown followed by RNA-seq of nuclear and mitochondrial genomes, with RSM22 knockdown as internal comparator

   PMID:36201550

   Open questions at the time

   • The opposing transcriptomic responses are correlative; the mechanistic basis of the non-redundancy is not defined
   • No direct assay of mitoribosome assembly state or rRNA processing
   • Whether transcript changes reflect assembly defects versus compensatory regulation is unresolved
4. 2022 Medium

   Demonstrating that late knockdown kills the parasite established MRPL23 as essential and placed its loss upstream of broad metabolic collapse.

   Evidence Conditional knockdown with RNA-seq and parasite viability assay

   PMID:36201550

   Open questions at the time

   • The broad transcriptional defects are downstream signatures, not a defined causal pathway to death
   • Essentiality shown by knockdown in one strain/stage; not tested across life-cycle stages
   • Single lab, single study

• The physical role of MRPL23 within the P. falciparum mitoribosome and its direct binding partners or RNA contacts remain undefined.
• No structural model or cryo-EM placement within the large subunit
• No direct rRNA- or protein-binding evidence
• No reciprocal validation of mitoribosome membership beyond localization and knockdown phenotypes