An EBA175 homologue which is transcribed but not translated in erythrocytic stages of Plasmodium falciparum.

Plasmodia species can bind to the Duffy blood group antigen (Plasmodium vivax and P. knowlesi) or glycophorin A (P. falciparum) on human erythrocytes as receptors for the invasion of merozoites in the asexual life cycle. A number of proteins have been identified in P. vivax, P. knowlesi and P. falciparum that serve as parasite ligands for these interactions and this group of proteins form the erythrocyte binding protein (EBP) family. The availability of sequence data generated as part of the P. falciparum Genome Project has allowed the identification of other genes related to the known EBP family members. We describe the Psi EBA165 gene and show that it has four exons, a structure identical to that described for EBA175. Analysis using reverse transcriptase-polymerase chain reaction (RT-PCR) has shown that all introns are spliced and that this gene is transcribed. The predicted protein would have the same structure as EBA175 containing the F1/F2 domains, a cysteine-rich region followed by a predicted transmembrane region and a short cytoplasmic tail, but the coding region of Psi EBA165 contains frameshifts. It was possible that the frameshifts may be corrected in the transcript, or alternatively, a mechanism could operate that allowed the translation machinery to read through the frameshifts. Antibodies that recognise EBA165 fusion proteins could not detect this protein in the P. falciparum parasites tested. Additionally, it was possible to disrupt the Psi EBA165 gene without affecting the parasite's ability to invade and grow in erythrocytes. These results suggest that the Psi EBA165 gene is a transcribed pseudogene.