Stage-dependent localization of a novel gene product of the malaria parasite, Plasmodium falciparum

A novel Plasmodium falciparum gene, MB2, was identified by screening a spor ozoite cDNA library with the serum of a human volunteer protected experimen tally by the bites of P, falciparum-infected and irradiated mosquitoes. The single-exon, single-copy MB2 gene is predicted to encode a protein with an M-r of 187,000. The MB2 protein has an amino-terminal basic domain, a cent ral acidic domain, and a carboxyl-terminal domain with similarity to the GT P-binding domain of the prokaryotic translation initiation factor 2. MB2 is expressed in sporozoites, the liver, and blood-stage parasites and gametoc ytes. The MB2 protein is distributed as a similar to 120-kDa moiety on the surface of sporozoites and is imported into the nucleus of blood-stage para sites as a similar to 66-kDa species. Proteolytic processing is favored as the mechanism regulating the distinct subcellular localization of the MB2 p rotein, This differential localization provides multiple opportunities to e xploit the MB2 gene product as a vaccine or therapeutic target.