Plasmodium falciparum-infected erythrocyte adhesion to the type 3 repeat domain of thrombospondin-1 is mediated by a modified band 3 protein

Previously, the binding site for the Plasmodium falciparum-infected erythro cyte (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 hav e localized the TSP binding site for PE more precisely. PE adhered to gluta thione-S-transferase-fusion proteins containing the type 3 repeat (T3) of T SP, but not to other functional domains of TSP (i.e. N-terminal domain, pro collagen domain, type 1 and 2 repeat, and C-terminal domain). Soluble T3 in hibited PE binding to immobilized TSP. PE binding to immobilized T3 was inh ibited by soluble TSP, a monoclonal antibody directed against the T3, glyci ne-arginine-glycine-aspartic acid-serine-proline (GRGDSP) peptide, and *cys teine-GRGDSP-cysteine*, where *cysteine and cysteine* form a disulfide link age, suggesting involvement of an RGD-containing motif in the T3. In suppor t of this, a fusion protein which excluded the RGD motif showed no PE bindi ng activity. Earlier it was shown that the amino acid sequence of the band 3 protein, histidine-proline-leucine-glutamine-lysine-threonine-tyrosine (H PLQKTY), was exposed on PE and mediated PE binding to TSP. Monoclonal antib odies, which recognize HPLQKTY and inhibit PE binding to TSP, also inhibite d PE binding to the T3. The involvement of the sequence was confirmed by th e fact that an octamer of HPLQKTY-containing peptide bound to the T3 but no t to the RGD motif-excluded fusion protein and the binding to T3 was inhibi ted 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. (C) 199 9 Elsevier Science B.V. All rights reserved.