Selection of yeast strains with enhanced expression of Plasmodium falciparum proteins.

The poor expression of Plasmodium falciparum proteins in heterologous systems and the difficulty in obtaining sufficient material directly from the parasite have limited the experimental characterization of many of the approximately 5200 proteins encoded by this organism. To improve the expression of P. falciparum proteins in the yeast Saccharomyces cerevisiae, we selected yeast ura3 mutants that acquired the ability to utilize the P. falciparum orthologue (PfOMPDC) of URA3 to grow on media lacking uracil. Two of these mutant strains, BY#29 and PJ#17, expressed up to 100-fold more of four P. falciparum proteins as a result of mutations in either HRP1 or KAP104, respectively. These mutations, as well as a temperature-sensitive rna15 mutation, likely decrease the efficiency of mRNA 3' end formation and produce longer mRNAs of P. falciparum genes. These yeast strains may be useful for the analysis and purification of P. falciparum proteins.