Abstract:
Hsp70 is a conserved molecular chaperone. How Hsp70 exhibits specialized functions across
species remains to be understood. Plasmodium falciparum Hsp70-1 (PfHsp70-1) and Escherichia coli
DnaK are cytosol localized molecular chaperones that are important for the survival of these two
organisms. In the current study, we investigated comparative structure-function features of PfHsp70-1
relative to DnaK and a chimeric protein, KPf, constituted by the ATPase domain of DnaK and the
substrate binding domain (SBD) of PfHsp70-1. Recombinant forms of the three Hsp70s exhibited
similar secondary and tertiary structural folds. However, compared to DnaK, both KPf and PfHsp70-1
were more stable to heat stress and exhibited higher basal ATPase activity. In addition, PfHsp70-1
preferentially bound to asparagine rich peptide substrates, as opposed to DnaK. Recombinant
P. falciparum adenosylmethionine decarboxylase (PfAdoMetDC) co-expressed in E. coli with either
KPf or PfHsp70-1 was produced as a fully folded product. Co-expression of PfAdoMetDC with
heterologous DnaK in E. coli did not promote folding of the former. However, a combination of
supplementary GroEL plus DnaK improved folding of PfAdoMetDC. These findings demonstrated
that the SBD of PfHsp70-1 regulates several functional features of the protein and that this molecular
chaperone is tailored to facilitate folding of plasmodial proteins.
