YihA2

PF3D7_1442200 (YihA2) is a mitochondrion-targeted GTPase of Plasmodium falciparum implicated in the assembly of the organellar ribosome (PMID:32057832). Recombinant PF3D7_1442200 localizes to the P. falciparum mitochondrion (PMID:32057832) and hydrolyzes GTP in vitro (PMID:32057832). It binds the large ribosomal subunit in a nucleotide-independent manner—engaging surrogate E. coli large subunits in vitro and co-immunoprecipitating with the P. falciparum mitochondrial large subunit (LSU) in vivo—placing it in complex with the mitoribosomal LSU (PMID:32057832). Beyond these findings, no functional consequence of GTP hydrolysis, no assembly intermediate, and no direct role for its positively charged C-terminal extension has been experimentally established in the available corpus.

1. 2020 Medium

   Establishing where PF3D7_1442200 acts: whether this GTP-binding protein operates in the parasite mitochondrion was unknown, and targeting experiments placed it in that organelle, framing it as a candidate factor for mitochondrial gene expression.

   Evidence Organelle targeting assay with recombinant protein in P. falciparum

   PMID:32057832

   Open questions at the time

   • Localization inferred from a recombinant targeting assay rather than endogenous tagging
   • Does not establish the specific submitochondrial context of function
2. 2020 Medium

   Confirming enzymatic identity: it was unknown whether the annotated GTP-binding protein is catalytically active, and an in vitro assay demonstrated GTPase activity, supporting a nucleotide-dependent functional cycle.

   Evidence In vitro GTPase activity assay with recombinant protein

   PMID:32057832

   Open questions at the time

   • Kinetic parameters and physiological triggers of hydrolysis not defined
   • Single method, single lab
3. 2020 Medium

   Assigning a molecular target: whether PF3D7_1442200 engages ribosomes was unknown, and binding to the large subunit in vitro together with in vivo co-IP of the mitochondrial LSU established it as a mitoribosome-associated factor acting independently of nucleotide state.

   Evidence In vitro binding to surrogate E. coli large subunits plus reciprocal in vivo co-immunoprecipitation with specific antibodies in P. falciparum

   PMID:32057832

   Open questions at the time

   • Direct assembly role vs. mere association not demonstrated by loss-of-function
   • In vitro binding used a heterologous E. coli ribosome surrogate
4. 2020 Low

   Probing structural specialization: the parasite mitoribosome has fragmented rRNA, and sequence analysis identified a positively charged C-terminal extension hypothesized to substitute for missing central-protuberance helices, but this role was not tested.

   Evidence Bioinformatic sequence/structural analysis without experimental validation

   PMID:32057832

   Open questions at the time

   • Structural role of the C-terminal extension is computational inference only, not experimentally confirmed
   • No mutagenesis of the charged stretch reported

• The physiological consequence of PF3D7_1442200's GTPase cycle for mitoribosome LSU maturation, and the functional role of its C-terminal extension, remain unresolved.
• No genetic knockout/knockdown phenotype
• No structure of the protein bound to the mitoribosome
• C-terminal extension function untested