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This Article ACCEPTED PREPRINT Full Text (PDF) All Versions of this Article: ps.036251.108v1 17/9/1494    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Curtidor, H. Articles by Patarroyo, M. E PubMed PubMed Citation Articles by Curtidor, H. Articles by Patarroyo, M. E Social Bookmarking                   What's this?

Characterisation of Plasmodium falciparum Integral Membrane Protein Pf25-IMP and Identification of its Red Blood Cell Binding Sequences Inhibiting Merozoite Invasion in vitro

¹ Universidad del Rosario and FIDIC;
² FIDIC and Universidad Nacional

(RECEIVED May 6, 2008; ACCEPTED June 9, 2008)

Abstract The identification of proteins present on the surface of Plasmodium falciparum-infected red blood cells as well as of free merozoites, has been widely considered as one of the main areas of research in the development of an anti-malarial vaccine due to their involvement in parasite's pathogenesis and invasion mechanisms. Major advances had been accomplished in this area thanks to the analysis of the reported genomic sequence of P. falciparum allowing for the identification of genes encoding for putative integral membrane proteins.This study reports for the first time the transcription of the MAL8P1.3 gene, which codifies for a 25-kDa-integral membrane protein of P. falciparum (FCB-2 strain) namely Pf25-IMP. Western blot and immunofluorescence assays using goat polyclonal sera indicate that this protein is expressed in erythrocytic asexual blood stages. A highly robust, sensible and specific receptor-ligand interaction assay allowed identifying two high activity binding peptides (HABPs) derived from Pf25-IMP: 30577 (41YKTANENVKLASSLSDRLSR60) and 30583 (161LNKKTVVRKIAEGLGYTIVF180). Both HABPs bound with high affinity to human red blood cells (RBCs), and such binding was susceptible to enzyme-treatment with trypsin. A common RBC surface receptor of apparently 48 kDa was found for both HABPs, plus an additional 31 kDa-receptor for HABP 30577. HABP 30577 inhibited merozoite invasion in vitro by 70% while HABP 30583 showed a 58% inhibition at 200 µM concentration.The data suggests a possible role of Pf25-IMP in merozoite invasion to RBCs and supports its inclusion in further immunological studies for evaluating its potential as vaccine candidates.

Keywords: Membrane Proteins; Structure; Electrophoresis; Active site/binding site/epitope mapping; Circular dichroism; Fluorescence; Immunological Methods; Synthesis of Peptides and Proteins

³ E-mail: hernando_curtidor{at}fidic.org.co

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