9YC3 | pdb_00009yc3

Crystal structure of malaria transmission-blocking antigen PfHAP2 domain 3 in complex with nanobody WNb 334

• PDB DOI: https://doi.org/10.2210/pdb9YC3/pdb

• Classification: PROTEIN BINDING
• Organism(s): Vicugna pacos, Plasmodium falciparum
• Expression System: Escherichia coli, Spodoptera frugiperda
• Mutation(s): No 


• Deposited: 2025-09-18 Released: 2025-12-31 
• Deposition Author(s): Lyons, F.M.T., Pymm, P., Dietrich, M.H., Tham, W.H.
• Funding Organization(s): National Health and Medical Research Council (NHMRC, Australia)

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.80 Å
• R-Value Free: 
  0.253 (Depositor), 0.253 (DCC) 
• R-Value Work: 
  0.224 (Depositor), 0.224 (DCC) 
• R-Value Observed: 
  0.225 (Depositor) 

Starting Models: in silico

Literature

Crystal structure and nanobodies against domain 3 of the malaria parasite fusogen Plasmodium falciparum HAP2.

Lyons, F.M.T., Chmielewski, J., Chan, L.J., Gabriela, M., Chan, R.W.B., Adair, A., Tong, J., Pymm, P., Zeglinski, K., Gouil, Q., Tham, W.H., Dietrich, M.H.

(2026) Biochem J 483

• PubMed: 41498187 
• DOI: https://doi.org/10.1042/BCJ20250297
• Primary Citation of Related Structures:  
  9YC3


• PubMed Abstract: 
  

  Malaria parasites are transmitted to humans through a bite from an infected female Anopheles mosquito. Within the mosquito midgut, malaria parasite gametes are activated and undergo fertilisation. If parasite fertilisation is perturbed, this stops the transmission of malaria parasites from mosquito to human. One proposed target of transmission-blocking interventions is Plasmodium falciparum fusogen PfHAP2, which is essential for gamete fusion during parasite fertilisation. However, to date, no monoclonal antibodies or structures of PfHAP2 have been generated. We have identified nanobodies that bind specifically to domain 3 of PfHAP2 with nanomolar affinities, two of which show some cross-species reactivity with HAP2 of other Plasmodium species. The crystal structure of one nanobody in complex with domain 3 of PfHAP2 provides the first structural insights into this transmission-blocking target in P. falciparum.

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Organizational Affiliation: 
• Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
WEHI, Melbourne, Australia.
Walter and Eliza Hall Institute of Medical Research Infectious Diseases and Immune Defence Division, Parkville, Australia.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 2-mer - A1B1 

Biological assembly 1 assigned by authors and generated by PISA (software)

Biological Assembly Evidence: gel filtration

Macromolecule Content 

• Total Structure Weight: 30.53 kDa 
• Atom Count: 1,792 
• Modeled Residue Count: 245 
• Deposited Residue Count: 276 
• Unique protein chains: 2

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Nanobody WNb 334	A	135	Vicugna pacos	Mutation(s): 0

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Male gamete fusion factor HAP2	B	141	Plasmodium falciparum	Mutation(s): 0  Gene Names: PF3D7_1014200
UniProt
Find proteins for Q8IJQ3 (Plasmodium falciparum (isolate 3D7)) Explore Q8IJQ3  Go to UniProtKB:  Q8IJQ3

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.80 Å
• R-Value Free:  0.253 (Depositor), 0.253 (DCC) 
• R-Value Work:  0.224 (Depositor), 0.224 (DCC) 
• R-Value Observed: 0.225 (Depositor) 

Space Group: P 3₂ 2 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 76.474	α = 90
b = 76.474	β = 90
c = 95.712	γ = 120

Software Package:

Software Name	Purpose
PHENIX	refinement
PDB_EXTRACT	data extraction
XDS	data reduction
XDS	data scaling
PHASER	phasing

Structure Validation

Entry History & Funding Information

Deposition Data

• Released Date: 2025-12-31 
Deposition Author(s): Lyons, F.M.T., Pymm, P., Dietrich, M.H., Tham, W.H.

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Funding Organization	Location	Grant Number
National Health and Medical Research Council (NHMRC, Australia)	Australia	APP2001385
National Health and Medical Research Council (NHMRC, Australia)	Australia	APP2016908

Revision History  

• Version 1.0: 2025-12-31
  Type: Initial release
  
• Version 1.1: 2026-01-21
  Changes: Database references
• Version 1.2: 2026-02-04
  Changes: Database references