PHB1

PHB1 (PF3D7_0829200) is an essential mitochondrial protein of Plasmodium that localizes to the branched mitochondrial network of P. falciparum asexual and sexual blood stages (PMID:37088154). Within the parasite mitochondrion it physically associates with PfPHB2, forming heterodimeric prohibitin complexes analogous to canonical inner-membrane PHB1–PHB2 assemblies (PMID:37088154, PMID:32883936). Its mitochondrial function is conserved: PHB1 rescues S. cerevisiae PHB1-deletion mutants, restoring mitochondrial DNA stability, mitochondrial integrity, and cell growth (PMID:37088154). In P. berghei the ortholog is refractory to genomic deletion, indicating that prohibitin function is required for blood-stage survival (PMID:29669282). PHB1 is the molecular target of the PHB inhibitor Rocaglamide, which suppresses growth of yeast strains complemented with PHB1 and inhibits P. falciparum asexual, gametocyte, and oocyst stages at nanomolar concentrations, marking PHB1 as a druggable antimalarial target (PMID:37088154). Beyond these observations, the precise biochemical role of PHB1 in maintaining the mitochondrial inner membrane has not been characterized in the available corpus.

1. 2018 Medium

   Establishing whether the Plasmodium prohibitin 1 ortholog is essential addressed whether it could serve as a viable drug target rather than a dispensable mitochondrial passenger.

   Evidence Fluorescence microscopy and attempted (unsuccessful) gene deletion in P. berghei

   PMID:29669282

   Open questions at the time

   • Essentiality shown in P. berghei, not directly in P. falciparum PHB1
   • Failed deletion does not reveal which mitochondrial function is required
   • No conditional knockdown to define the essential process
2. 2020 Low

   Testing whether PHB1 partners with PHB2 addressed whether the parasite builds heterodimeric prohibitin complexes like canonical eukaryotes.

   Evidence Yeast two-hybrid analysis with homology modelling

   PMID:32883936

   Open questions at the time

   • Single method (yeast two-hybrid) with no in-parasite biochemical validation in this study
   • Supercomplex stoichiometry inferred from homology, not measured
   • No structure of the parasite complex
3. 2023 Medium

   Determining PHB1's subcellular location and its physical interaction with PfPHB2 in parasites confirmed it is a bona fide mitochondrial prohibitin acting in a complex, not an isolated protein.

   Evidence Immunostaining, subcellular fractionation, and co-immunoprecipitation in P. falciparum 3D7

   PMID:32883936 PMID:37088154

   Open questions at the time

   • Co-IP does not resolve direct versus indirect contact or complex architecture
   • Other complex members not identified
   • Interaction not mapped to specific domains
4. 2023 Medium

   Heterologous complementation established that PHB1 carries out a conserved mitochondrial function, defining its cellular role in mtDNA stability and organellar integrity.

   Evidence Functional complementation of S. cerevisiae PHB1-deletion mutants with multiple phenotypic readouts

   PMID:37088154

   Open questions at the time

   • Function inferred from yeast rescue, not directly demonstrated in the parasite
   • Biochemical mechanism of mtDNA stabilization unresolved
   • Native substrates or client proteins unidentified
5. 2023 Medium

   Identifying PHB1 as the molecular target of Rocaglamide connected the mitochondrial protein to a chemically tractable, transmission-blocking antimalarial strategy.

   Evidence Rocaglamide inhibition of PHB1-complemented yeast plus P. falciparum growth assays across asexual, gametocyte, and oocyst stages

   PMID:37088154

   Open questions at the time

   • Direct binding of Rocaglamide to parasite PHB1 not demonstrated biochemically
   • Whether Roc-A engages the PHB1–PHB2 complex or PHB1 alone unclear
   • Resistance mechanisms and target selectivity not defined
6. 2026 Low

   Placing PHB1 among the four mitochondrial SPFH proteins situated it within a broader membrane-scaffold family sharing the organelle.

   Evidence Epitope tagging and fluorescence microscopy in a comparative SPFH family study

   PMID:41662436

   Open questions at the time

   • PHB1-specific functional data not provided beyond mitochondrial localization
   • Functional relationship among the SPFH proteins not established for PHB1
   • Study focus was on a different SPFH member

• The direct in-parasite biochemical function of PHB1 — its native complex architecture, molecular substrates, and mechanism of maintaining mitochondrial DNA and membrane integrity — remains undefined.
• No structural model of the parasite PHB1–PHB2 complex
• No direct demonstration of mtDNA/integrity function in the parasite itself
• Direct Rocaglamide–PHB1 binding not shown