Interaction of the exported malaria protein Pf332 with the red blood cell membrane skeleton

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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 (Kd = 0.60 µM) 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.

Abbreviations

RBC
red blood cell
IRBC
infected red blood cell
Pf332 or Ag332
Plasmodium falciparum Antigen 332
Kd
half saturation concentration
4.1R
red blood cell protein 4.1
GPC and GPD
glycophorins C and D, respectively
PfEMP1
Plasmodium falciparum erythrocyte membrane protein 1
KAHRP
knob-associated histidine rich protein
MESA
mature parasite-infected erythrocyte surface antigen
RESA
ring-infected erythrocyte surface antigen
PfEMP3
Plasmodium falciparum erythrocyte membrane protein 3
PV
parasitophorous vacuole
PEXEL
Plasmodium export element
VTS
vacuolar transport signal
PVM
parasitophorous vacuolar membrane
MCs
Maurer's clefts
IOV and pIOV
inside-out vesicle prepared from normal RBCs or parasite-infected RBCs
PCR
polymerase chain reaction
MBP
maltose-binding protein
PBS
phosphate-buffered saline
IB
IOV incubation buffer
BSA
bovine serum albumin
PVDF
Polyscreen® polyvinylidene difluoride
TX100
Triton X-100
DBL
Duffy binding-like domain

Keywords

Plasmodium falciparum
Malaria
Pf332
Actin
Red blood cell
Membrane skeleton

Cited by (0)

1

Joint senior authors.