POFUT2

POFUT2 (PF3D7_0909200) is a GDP-fucose protein O-fucosyltransferase that O-glycosylates thrombospondin type I repeat (TSR)-containing sporozoite surface proteins, including CSP and TRAP, and its activity governs the folding, stability, and trafficking of these adhesins required for the mosquito and liver stages of the malaria life cycle (PMID:28916755). In P. falciparum, genetic disruption of POFUT2 destabilizes and mistraffics TSR-bearing proteins, placing the enzyme within a non-canonical glycosylation-dependent ER protein quality control mechanism, and attenuates ookinete midgut colonization, sporozoite gliding motility, cell traversal, hepatocyte invasion, and exoerythrocytic development (PMID:28916755). The phenotypic requirement diverges across species: in P. berghei, one study found null mutants with no motility defect and normal blood-stage infection (PMID:31334132), whereas another reported reduced TRAP levels, impaired gliding, and diminished hepatocyte infectivity with normal blood and mosquito stages, and molecular dynamics indicated O-fucosylation stabilizes the TSR domain structure without altering heparin binding (PMID:38421807). Beyond these genetic and structural analyses, the enzymatic details of POFUT2 catalysis have not been characterized in the available corpus.

1. 2003 Low

   Before any Plasmodium-specific function was known, the question was how POFUT2 relates to other fucosyltransferases; sequence analysis placed it in a fucosyltransferase superfamily sharing conserved motifs, framing it as a candidate O-fucosyltransferase.

   Evidence Phylogenetic analysis and conserved peptide motif identification across fucosyltransferase families

   PMID:12966037

   Open questions at the time

   • Computational/comparative only — no in vitro or in vivo functional experiment on the Plasmodium protein
   • Enzymatic activity and substrate specificity not tested
   • No cellular localization or life-cycle role established
2. 2017 High

   The central question of what POFUT2 does in the parasite was answered by showing it O-fucosylates the TSR proteins CSP and TRAP, and that this modification is required for their stability, trafficking, and for transmission-relevant stages of the life cycle.

   Evidence Genetic knockout in P. falciparum with life-cycle-wide phenotyping (motility, traversal, hepatocyte invasion, humanized-mouse infection) plus assessment of CSP/TRAP stability and trafficking

   PMID:28916755

   Open questions at the time

   • In vitro enzymatic characterization (kinetics, GDP-fucose donor use) not reported
   • Full repertoire of TSR-protein substrates beyond CSP and TRAP not defined
   • Molecular details of the ER quality-control link not resolved
3. 2019 Medium

   To test whether the P. falciparum requirement generalizes, POFUT2 was disrupted in the rodent model P. berghei; the null mutant showed no motility defect and normal blood-stage infection, indicating O-fucosylation is not essential in this species.

   Evidence Null-mutant generation in P. berghei with sporozoite motility assays and mouse infection

   PMID:31334132

   Open questions at the time

   • Single-lab result that contradicts P. falciparum findings and a later P. berghei study
   • TRAP/CSP protein levels not quantified in this study
   • Reason for species divergence not explained
4. 2024 Medium

   A second P. berghei study revisited the requirement and found that POFUT2 disruption reduces TRAP levels and impairs gliding and hepatocyte infectivity, with MD simulation indicating O-fucosylation stabilizes the TSR fold rather than affecting heparin binding.

   Evidence POFUT2 knockout in P. berghei with TRAP quantification, gliding and invasion assays, and all-atom MD simulation of the TSR domain

   PMID:38421807

   Open questions at the time

   • Partially contradicts the earlier P. berghei report; source of discrepancy unresolved
   • MD simulation is computational and hypothesis-generating, not experimental structure
   • Direct enzymatic modification of TRAP not biochemically demonstrated here

• The biochemical basis of POFUT2 catalysis and the source of the P. berghei phenotypic discrepancy remain unresolved.
• No in vitro reconstitution of POFUT2 enzymatic activity or donor/acceptor kinetics
• No experimental structure of POFUT2 or the enzyme-substrate complex
• Species divergence between P. falciparum requirement and conflicting P. berghei reports not mechanistically explained