Two Plasmodium falciparum genes express merozoite proteins that are related to Plasmodium vivax and Plasmodium yoelii adhesive proteins involved in host cell selection and invasion

Two related Plasmodium falciparum genes and their encoded proteins have bee n identified by comparative analyses with Plasmodium vivax reticulocyte bin ding protein 2 (PvRBP-2). The P. falciparum genes have a structure which su ggests that they may be the result of an evolutionary duplication event, as they share more than 8 kb of closely related nucleotide sequence but then have quite divergent unique 3' ends. Between these shared and unique region s is a complex set of repeats, the nature and number of which differs betwe en the two genes, as well as between different P. falciparum strains. Both genes encode Targe hydrophilic proteins, which are concentrated at the inva sive apical end of the merozoite and are predicted to be more than 350 kDa, with an N-terminal signal sequence and a single transmembrane domain near their C termini. importantly, they also share gene structure and amino acid homology with the Plasmodium yoelii 235-kDa rhoptry protein family, which is also related to PvRBP-2. Together these Plasmodium proteins define an ex tended family of proteins that appear to function in erythrocyte selection and invasion. As such, they may prove to be essential components of malaria vaccine preparations.