Functional studies of atypical caseinolytic protease subunits from Plasmodium falciparum

Abstract

Caseinolytic protease (Clp) complex plays important roles in regulating the pathogenicity, survival and development of various organisms, but its role in the pathogenicity of Plasmodium falciparum has not been investigated. This study aimed to characterize two putative plasmodial Clp protease subunits, PfClpP1 and PfClpP2. Six different PfClpP constructs were designed and expressed using E. coli and mammalian cell lines. Heterologous expression studies showed that signal peptides hindered expression of full length PfClpPs in the E. coli but do not affect their expression in the mammalian cells. Biochemical analyses of the bacterial-expressed PfClpP1- and PfClpP2-GST fusion proteins revealed differences in their substrate preferences. While eukaryotic ClpPs were reported to be localized to mitochondria and chloroplasts, PfClpP1 proteins were localized to the mammalian cell nuclei when tested using a mammalian surrogate host. In conclusion, the substrate preference and sub-cellular localization of PfClpPs are unique among their homologs.