PF3D7_0305700

PF3D7_0305700 is an active E2-conjugating enzyme of Plasmodium falciparum that operates in both the SUMO and ubiquitin conjugation systems during asexual blood-stage development (PMID:26697886, PMID:40249735). In the SUMO pathway, it functions as the E2-conjugating enzyme that engages the P. falciparum SUMO E1-activating enzyme through surface residues distinct from the human E1–E2 interface (PMID:26697886), and this SUMOylation activity contributes to protecting trophozoite-stage parasites against iron-induced oxidative stress (PMID:26697886). The parasite enzyme also displays species-specific SUMO recognition: whereas Pf-SUMO can engage human E2, Hs-SUMO1 fails to interact with PF3D7_0305700, a selectivity governed by critical N-terminal residues whose mutation to the human counterparts restores the cross-species interaction (PMID:35331687). In the ubiquitin pathway, PF3D7_0305700 was captured as a catalytically active E2 by a ubiquitin activity-based probe and validated in vitro, and it shows selective functional interaction with the HECT E3 ligase PfHEUL (PMID:40249735). Beyond these activities, the enzyme's full substrate repertoire and its in vivo genetic requirement remain uncharacterized in the available corpus.

1. 2015 High

   Establishing how the parasite SUMO E2 engages its E1 partner was needed to define whether the conjugation interface diverges from the human system and could be selectively targeted; crystallography plus mutagenesis showed the P. falciparum E1–E2 interaction uses surface residues distinct from the human interface.

   Evidence X-ray crystallography of the human E1 ubiquitin fold domain–Ubc9 complex with in silico modeling, site-directed mutagenesis, and in vitro biochemistry of the P. falciparum enzymes

   PMID:26697886

   Open questions at the time

   • No crystal structure of the P. falciparum E1–E2 complex itself
   • SUMO substrates conjugated via this E2 not identified
2. 2015 Medium

   It was unclear whether SUMOylation had a defined physiological role in blood-stage parasites; oxidative-stress assays linked SUMOylation pathway activity, in which PF3D7_0305700 acts as the E2, to protection of trophozoites under iron-induced oxidative stress.

   Evidence Cell-based oxidative stress assays on asexual blood-stage P. falciparum

   PMID:26697886

   Open questions at the time

   • Indirect readout without direct genetic perturbation of PF3D7_0305700
   • Protective mechanism and relevant SUMOylated targets undefined
3. 2022 Medium

   To determine the structural basis of SUMO recognition specificity, cross-species interaction tests asked whether parasite and human components are interchangeable; they revealed a unidirectional interaction in which Hs-SUMO1 fails to engage PF3D7_0305700 owing to critical N-terminal residues, restorable by humanizing those residues.

   Evidence Biochemical and biophysical interaction analyses with site-directed mutagenesis and reciprocal cross-species interaction tests

   PMID:35331687

   Open questions at the time

   • Consequences of the specificity for in vivo SUMO conjugation not tested
   • Single-lab biophysical characterization
4. 2025 Medium

   Whether PF3D7_0305700 also acts as a bona fide ubiquitin E2 in living parasites was open; activity-based probe capture during blood-stage growth plus in vitro ubiquitination confirmed it as an active ubiquitin-conjugating enzyme with selective interaction with the HECT E3 PfHEUL.

   Evidence Activity-based protein profiling with a Ub-Dha probe during P. falciparum asexual development and in vitro ubiquitination assays

   PMID:40249735

   Open questions at the time

   • Ubiquitination substrates and chain topology not defined
   • Functional consequence of the PfHEUL interaction in vivo untested
   • Single study, single lab

• It remains unknown whether PF3D7_0305700 is genetically essential and what its physiological substrate set is across the SUMO and ubiquitin pathways in the intact parasite.
• No conditional knockdown or knockout phenotype reported
• No in vivo substrate identification
• Relative contribution of SUMO versus ubiquitin conjugation roles undetermined