title: High affinity interactions between red blood cell receptors and synthetic Plasmodium thrombospondin-related apical merozoite protein (PTRAMP) peptides.
abstract: Plasmodium falciparum thrombospondin-related apical merozoite protein (PTRAMP) has a thrombospondin related (TSR) domain which in many proteins has been reported as a fragment involved in pathogen-host and cell-interactions. Receptor-ligand studies using eighteen non-overlapping 20-aminoacid-long synthetic peptides from this protein were carried out to determine regions involved in parasite invasion of red blood cells (RBC). Two high activity binding peptides (HABPs) were determined, 33405 (21YISSNDLTSTNLKVRNNWEH40) and 33413 (180LEGPIQFSLGKSSGAFRINY199), presenting high dissociation constants and positive cooperativity. One of the HABPs displayed a modified Plasmodium export element (PEXEL), suggesting that this protein could be involved in the merozoite cytoplasmic reticulum, parasitophorous vacuole, red blood cell (RBC) cytosol, and probably infected RBC (iRBC) membrane transport of some other molecules and nutrients. Enzymatic treatment of RBCs increased HABP 33405 binding to them whilst it decreased HABP 33413 binding. Merozoite invasion assays revealed that HABPs have around 57% ability to inhibit new RBC invasion. Circular dichroism revealed the presence of possible alpha-helical elements in both HABPs structures. RBC binding interaction specificity and the presence of a PEXEL motif make these 2 HABPs good candidates for being included in further studies to develop a new multi-antigenic, multi-stage, subunit-based, chemically-synthesised, anti-malarial vaccine.
authors.affiliation: Fundación Instituto de Inmunología de Colombia, Bogotá, Colombia.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Calderón
authors.forename: Hernando
authors.initials: H
authors.lastname: Curtidor
authors.forename: Oscar
authors.initials: O
authors.lastname: González
authors.forename: Gladys
authors.initials: G
authors.lastname: Cifuentes
authors.forename: Claudia
authors.initials: C
authors.lastname: Reyes
authors.forename: Manuel E
authors.initials: ME
authors.lastname: Patarroyo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D004910:Erythrocyte Membrane / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010961:Plasmodium / Q000378:metabolism*; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D008565:Membrane Proteins; C487867:PTRAMP protein, Plasmodium; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface