Identification and characterization of putative erythrocyte binding protein genes in Plasmodium falciparum
Drummond, Paul Bassanio
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The erythrocyte binding proteins (EBP) of Plasmodium falciparum are ligands that play a functional role in erythrocyte invasion by merozoites. Six EBP genes have already been identified in the P. falciparum genome. However, their role in invasion and potential interaction is not completely understood. A series of experimental studies were conducted to identify, and to characterize these EBP genes. A Polymerize Chain Reaction (PCR) approach was used to identify potential EBP genes in two P. falciparum isolates. Several clones sequenced were known EBP genes, which validated our approach to identified novel members of the EBP family. However, research to determine the identity of these sequences is on going. A study was designed to investigate the level of sequence conservation within the Duffy binding-like domains of one member of the EBP family, the erythrocyte binding-like 1 (EBL-1) gene in ten P. falciparum isolates. The result indicates a degree of polymorphism in the Duffy binding-like domains comparable to that observed for erythrocyte binding antigen-175 (a member of the EBP family). Additionally, there was a clear bias towards nonsynonymous substitution in the EBL-1 Duffy binding-like domains. Our result obtained from this study suggests that ebl-1 is not essential in some isolates. The results suggest that the diversity observed in the Duffy binding-like region of the ebl-1 gene in P.falciparum may either be driven by host immune response, or may indicate receptor heterogeneity. The final goal of this work was a comprehensive study of EBP gene expression during the intraerythrocytic developmental cycle in three P. falciparum isolates. Our results show that expression of EBPs is highly stage specific, with expression peaking at 36-hr in the 3D7 and Dd2 isolate, and at 44-hr in the Dd2-NM clone. We also found that eba-175 had the highest level of expression, while maebl was the least expressed in all three isolates. We also found one gene that is not expressed in all isolates.