CDNA cloning of a novel cysteine protease of Plasmodium falciparum

Abstract

The cDNA for a novel Plasmodium cysteine protease (falcipain-2) has been isolated from a Plasmodium falciparum cDNA library. A 602 bp fragment was amplified from P. falciparum by PCR using degenerate oligonucleotide primers. The primers were designed based upon the amino acids flanking the active site cysteine and asparagine residues that are conserved in the eukaryotic cysteine proteases. This fragment was used to screen a P. falciparum cDNA library and isolated a 2.1 kb clone that encoded a novel cysteine protease. The sequence of the 2.1 kb clone predicted a 56 kDa protein containing a typical signal sequence, a prosequence and a 24.7 kDa mature protease with 37% identity to falcipain-1, a hemoglobin-degrading cysteine protease of P. falciparum. Northern blot analysis detected a 2.1 kb message in trophozoites. Taken together, we have isolated a novel cysteine protease of P. falciparum, which may play an important role at the late stages of the erythrocytic cycle of the parasite.