Characterization of the merozoite surface protein 4/5 gene of Plasmodium berghei and Plasmodium yoelii

The genes encoding merozoite surface protein 4/5 (MSP4/5) from Plasmodium berghei and Plasmodium yoelii have been cloned and completely sequenced. Comparisons of the predicted protein sequences with those of Plasmodium chabaudi MSP4/5 and Plasmodium falciparum MSP4 and MSP5 show general structural similarities. All predicted proteins contain hydrophobic signal sequences, potential GPI attachment sequences and a single epidermal growth factor (EGF)-like domain at the C-terminus. The amino acid sequence of the EGF-like motif is highly conserved in rodent malaria species and also shows a considerable degree of similarity with the EGF-like domains found in the P. falciparum proteins. Both the P. yoelii and P. berghei genes show evidence of both spliced and unspliced mRNA at steady state. This phenomenon is similar to that seen for the P. chabaudi MSP4/5 gene, and is believed to be involved in regulation of protein expression. We describe here the construction of clones expressing full length recombinant protein. Antibodies directed against recombinant MSP4/5 proteins recognize a single polypeptide on parasite material and show crossreactivity between MSP4/5 from different murine malaria species, but do not crossreact with either MSP4 or MSP5 from P. falciparum. The various antisera show reactivity against reduction sensitive epitopes as well as reduction insensitive epitopes.