title: Folding of the Plasmodium falciparum cysteine protease falcipain-2 is mediated by a chaperone-like peptide and not the prodomain.
abstract: Papain-family cysteine proteases of the malaria parasite Plasmodium falciparum, known as falcipains, are hemoglobinases and potential drug targets. Available data suggest that papain-family proteases require prodomains for correct folding into functional conformations. However, in prior studies of falcipain-2, an Escherichia coli-expressed construct containing only a small portion of the prodomain refolded efficiently, suggesting that this enzyme differs in this regard from other papain-family enzymes. To better characterize the determinants of folding for falcipain-2, we expressed multiple pro- and mature constructs of the enzyme in E. coli and assessed their abilities to refold. Mature falcipain-2 refolded into active protease with very similar properties to those of proteins resulting from the refolding of proenzyme constructs. Deletion of a 17-amino acid amino-terminal segment of the mature protease yielded a construct incapable of correct folding, but inclusion of this segment in trans allowed folding to active falcipain-2. The prodomain was a potent, competitive, and reversible inhibitor of mature falcipain-2 (K(i) 10(-10) m). Our results identify a chaperone-like function of an amino-terminal segment of mature falcipain-2 and suggest that protease inhibition, but not the mediation of folding, is a principal function of the falcipain-2 prodomain.
authors.affiliation: Department of Medicine, San Francisco General Hospital, University of California, San Francisco, California 94143, USA.
authors.forename: Puran S
authors.initials: PS
authors.lastname: Sijwali
authors.forename: Bhaskar R
authors.initials: BR
authors.lastname: Shenai
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Rosenthal
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002384:Catalysis; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000201:enzymology*; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D018832:Molecular Chaperones; D003546:Cysteine Endopeptidases; C416224:falcipain 2