Isolation and characterization of type I signal peptidase of different malaria parasites

Type I signal peptidases are important membrane-bound serineproteases responsible for the cleavage of the signal peptide ofthe proteins. These enzymes are unique serine proteases thatcarry out catalysis using a serine/lysine catalytic dyad. In thepresent study, we report the isolation of type I signal peptidasefrom the malaria parasites Plasmodium falciparum,Plasmodium knowlesi, and Plasmodium yoelii andsome characterization of type I signal peptidase ofPlasmodium falciparum. We show that these enzymes arehomologous to signal peptidases from various sources and alsocontain the conserved boxes present in other type I signalpeptidases. The type I signal peptidase from P falciparumis an intron-less and a single-copy gene. The results also showthat the enzyme from Plasmodium falciparum is subject toself-cleavage and it has been demonstrated to possess type Isignal peptidase activity in E coli preprotein processingin vivo by complementation assay. This study will be helpful inunderstanding one of the important metabolic pathways “thesecretory pathway” in the parasite and should make an importantcontribution in understanding the complex process of proteintargeting in the parasite.