Promiscuous stimulation of HSP70 ATPase activity by parasite-derived J-domains

The malaria parasite P. falciparum exports a large number of proteins to the human host cell, including members of the J-domain protein (JDP) family. In other systems, JDPs stimulate the ATPase activity of HSP70 and direct client protein interactions. Three exported PfJDP are highly homologous yet appear to have divergent roles. We examined the ability of isolated J-domains from these proteins to stimulate the ATPase activity of PfHSP70-X and human HsHSP70 and HsHSC70. In vitro assays demonstrate that all domains stimulate the ATPase activity of each HSP70 tested. While overall stimulation was broadly comparable, differences were observed between individual PfJDP-HSP70 pairings. Our findings support a model in which the parasite systematically exports JDPs to exploit the host's chaperone power.