HEP1

HEP1 (PF3D7_1420300) is a DNL-type zinc finger protein in Plasmodium falciparum that functions as a chaperone-escort factor for the mitochondrial-type chaperone PfHsp70-3 (PMID:27253881). Co-expression of HEP1 with PfHsp70-3 enhances the solubility of the chaperone, and HEP1 specifically suppresses the thermally induced aggregation of PfHsp70-3 but not of unrelated substrates such as malate dehydrogenase or citrate synthase, establishing substrate specificity for PfHsp70-3 (PMID:27253881). This escort activity depends on zinc coordination: chelation of zinc with EDTA abolishes HEP1's ability to prevent PfHsp70-3 aggregation, indicating that an intact DNL-type zinc finger is required for function (PMID:27253881). Beyond this in vitro anti-aggregation activity toward PfHsp70-3, no further mechanistic detail — including cellular localization, in vivo function, or essentiality — has been characterized for PF3D7_1420300 in the available corpus.

1. 2016 Medium

   Whether P. falciparum encodes a functional Hep1-type escort protein and which chaperone it acts on was unknown; identifying HEP1 as a specific anti-aggregation partner of PfHsp70-3 established its role as a chaperone-escort protein.

   Evidence Co-expression in a heterologous system and in vitro thermal aggregation suppression assays with specificity controls (MDH, citrate synthase)

   PMID:27253881

   Open questions at the time

   • Not tested in vivo in the parasite; cellular localization and essentiality not addressed
   • Direct physical binding stoichiometry/affinity to PfHsp70-3 not resolved
   • Single lab, single study
2. 2016 Medium

   Whether the DNL-type zinc finger is functionally required was unknown; demonstrating that zinc chelation abolishes anti-aggregation activity established zinc coordination as essential for HEP1 escort function.

   Evidence In vitro aggregation suppression assay with EDTA-mediated zinc chelation

   PMID:27253881

   Open questions at the time

   • EDTA chelation is a bulk perturbation; specific zinc-coordinating residues not mutationally defined
   • Structural basis of zinc-dependent PfHsp70-3 engagement not determined
   • Single lab, single study

• The in vivo role of PF3D7_1420300 in the parasite — its subcellular localization, requirement for PfHsp70-3 function during the life cycle, and essentiality — remains uncharacterized.
• No in-parasite genetic or localization data in the corpus
• No structural model of the HEP1–PfHsp70-3 interaction
• Zinc-coordinating residues not individually mapped