Cloning and characterization of a Plasmodium falciparum gene encoding a novel high-molecular weight host membrane-associated protein, PfEMP3

Mol Biochem Parasitol. 1993 May;59(1):59-72. doi: 10.1016/0166-6851(93)90007-k.


The rat monoclonal antibody, mAb 12C11, reacts with numerous proteins from mature asexual stages of Plasmodium falciparum. The largest is 315 kDa and is designated PfEMP3. A lambda gt11 expression library, generated from genomic DNA of Malayan Camp strain parasites, was screened with mAb 12C11. One positive clone, lambda 12.1.3, contained a 1.4-kb fragment in frame with the beta-galactosidase gene of lambda gt11. The deduced 455-amino acid sequence is a novel, highly charged sequence encoding two 15-amino acid repeats at the N-terminus followed by 27 repeats of 13 amino acids. The last 59 C-terminal residues are non-repetitive. Two in-frame stop codons at the 3' end of the DNA suggests that this DNA fragment encodes the C-terminus of the protein. Southern blotting with the cloned fragment identified two copies of this fragment per haploid genome in knob-positive, parasitized erythrocytes (K+PE). Both DNA fragments are absent from K - PE. Northern blotting of trophozoite-stage PE total RNA revealed mRNAs of 10, 4.4 and 2 kb in K+PE, but no hybridization with K - PE. Immune sera were elicited against the lambda 12.1.3 beta-galactosidase fusion protein and peptides generated from the predicted lambda 12.1.3 amino acid sequence. These sera and mAb 12C11 reacted specifically with PfEMP3 in Western blots of mature K+PE but not with K - PE. Rat and mouse sera against the recombinant protein produced an immunofluorescence pattern in fixed mature K+PE almost identical to the pattern produced by a monoclonal antibody against the knob-associated protein, Histidine Rich Protein 1. The same antibodies were immunofluorescence negative with fixed K - PE. Mouse antibodies against the recombinant protein reacted on immunoelectron microscopy with the erythrocyte membrane of K+PE, labeling knobs as well as the membrane between knobs. In contrast, a mAb against Histidine Rich Protein 1 reacted only under the electron dense material of knobs. We conclude that the lambda 12.1.3 clone encodes the C-terminal portion of the 315 kD PfEMP3 antigen and that PfEMP3 may be involved in knob formation or other perturbations of the erythrocyte membrane.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies, Monoclonal
  • Base Sequence
  • Cloning, Molecular
  • DNA, Protozoan / genetics
  • Erythrocyte Membrane / parasitology
  • Genes, Protozoan*
  • Humans
  • Malaria, Falciparum / parasitology
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / immunology
  • Molecular Sequence Data
  • Molecular Weight
  • Peptide Fragments / genetics
  • Peptide Fragments / immunology
  • Plasmodium falciparum / genetics*
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics*
  • Protozoan Proteins / immunology


  • Antibodies, Monoclonal
  • DNA, Protozoan
  • Membrane Proteins
  • Peptide Fragments
  • Protozoan Proteins

Associated data

  • GENBANK/X67701