title: Plasmodium falciparum-infected erythrocyte adhesion to the type 3 repeat domain of thrombospondin-1 is mediated by a modified band 3 protein.
abstract: Previously, the binding site for the Plasmodium falciparum-infected erythrocyte (PE) was determined to be the C-terminal 120 or 140 kDa region but not the N-terminal 25 kDa domain of thrombospondin (TSP). In this work, we have localized the TSP binding site for PE more precisely. PE adhered to glutathione-S-transferase-fusion proteins containing the type 3 repeat (T3) of TSP, but not to other functional domains of TSP (i.e. N-terminal domain, procollagen domain, type 1 and 2 repeat, and C-terminal domain). Soluble T3 inhibited PE binding to immobilized TSP. PE binding to immobilized T3 was inhibited by soluble TSP, a monoclonal antibody directed against the T3, glycine-arginine-glycine-aspartic acid-serine-proline (GRGDSP) peptide, and *cysteine-GRGDSP-cysteine*, where *cysteine and cysteine* form a disulfide linkage, suggesting involvement of an RGD-containing motif in the T3. In support of this, a fusion protein which excluded the RGD motif showed no PE binding activity. Earlier it was shown that the amino acid sequence of the band 3 protein, histidine-proline-leucine-glutamine-lysine-threonine-tyrosine (HPLQKTY), was exposed on PE and mediated PE binding to TSP. Monoclonal antibodies, which recognize HPLQKTY and inhibit PE binding to TSP, also inhibited PE binding to the T3. The involvement of the sequence was confirmed by the fact that an octamer of HPLQKTY-containing peptide bound to the T3 but not to the RGD motif-excluded fusion protein and the binding to T3 was inhibited by GRGDSP peptide. Thus, PE binding to the T3 domain of TSP is mediated by the peptidic sequence HPLQKTY of band 3 which is exposed on PE.
authors.affiliation: Department of Biology, University of California, Riverside 92521, USA.
authors.forename: S
authors.initials: S
authors.lastname: Eda
authors.forename: J
authors.initials: J
authors.lastname: Lawler
authors.forename: I W
authors.initials: IW
authors.lastname: Sherman
mesh_terms: D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D000911:Antibodies, Monoclonal; D001665:Binding Sites; D002448:Cell Adhesion; D004912:Erythrocytes / Q000378:metabolism* / Q000469:parasitology*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology; D009842:Oligopeptides / Q000378:metabolism; D010963:Plasmodium falciparum / Q000302:isolation & purification / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019700:Thrombospondin 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D000911:Antibodies, Monoclonal; D009842:Oligopeptides; D011993:Recombinant Fusion Proteins; D019700:Thrombospondin 1; D005982:Glutathione Transferase