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Interaction of the exported malaria protein Pf332 with the red blood cell membrane skeleton
Karena L Waller1, Lisa M Stubberfield, Valentina Dubljevic
1Department of Microbiology, Monash University, VIC 3800, Australia.
Abstract:
Intra-erythrocytic Plasmodium falciparum malaria parasites synthesize and export numerous proteins into the red blood cell (RBC) cytosol, where some bind to the RBC membrane skeleton. These interactions are responsible for the altered antigenic, morphological and functional properties of parasite-infected red blood cells (IRBCs). Plasmodium falciparum protein 332 (Pf332) is a large parasite protein that associates with the membrane skeleton and who's function has recently been elucidated. Using recombinant fragments of Pf332 in in vitro interaction assays, we have localised the specific domain within Pf332 that binds to the RBC membrane skeleton to an 86 residue sequence proximal to the C-terminus of Pf332. We have shown that this region partakes in a specific and saturable interaction with actin (K(d)=0.60 microM) but has no detectable affinity for spectrin. The only exported malaria protein previously known to bind to actin is PfEMP3 but here we demonstrate that there is no competition for actin-binding between PfEMP3 and Pf332, suggesting that they bind to different target sequences in actin.
Insights
Plasmodium falciparum malaria parasites export proteins that alter red blood cells. Researchers identified a specific region in Pf332 protein that binds to red blood cell actin, distinct from PfEMP3.
Area of Science:
- Molecular parasitology
- Cell biology
- Protein-biochemistry
Background:
- Intra-erythrocytic malaria parasites, Plasmodium falciparum, export proteins into red blood cells (RBCs).
- These exported proteins interact with the RBC membrane skeleton, altering infected RBC properties.
- Plasmodium falciparum protein 332 (Pf332) is a known RBC membrane-associated parasite protein.
Purpose of the Study:
- To elucidate the function of Plasmodium falciparum protein 332 (Pf332).
- To identify the specific domain of Pf332 responsible for binding to the red blood cell (RBC) membrane skeleton.
- To characterize the interaction of Pf332 with RBC cytoskeletal components.
Main Methods:
- In vitro interaction assays using recombinant fragments of Pf332.
- Biochemical characterization of protein-ligand binding kinetics.
- Competition assays to assess binding site specificity.
Main Results:
- A specific 86-residue sequence near the C-terminus of Pf332 binds to the RBC membrane skeleton.
- This region exhibits a specific and saturable interaction with actin (K(d)=0.60 microM).
- Pf332 binding to actin does not compete with PfEMP3, indicating distinct binding sites.
Conclusions:
- The C-terminal region of Pf332 mediates interaction with red blood cell actin.
- Pf332 and PfEMP3 bind to different sites on actin, suggesting independent functional roles.
- Understanding these interactions is crucial for comprehending malaria pathogenesis and infected RBC alterations.
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