title: Biochemical characterization of the apicoplast-targeted AAA+ ATPase ClpB from Plasmodium falciparum.
abstract: ClpB is a molecular chaperone from the AAA+ superfamily of ATPases, which reactivates aggregated proteins in cooperation with the DnaK chaperone system. ClpB is essential for infectivity and in-host survival of a number of pathogenic microorganisms, but systematic studies on ClpB from pathogens have not been reported yet. We purified and characterized one of the two ClpB isoforms from the malaria parasite Plasmodium falciparum, PfClpB1. PfClpB1 is targeted to the apicoplast, an essential plastid organelle that is a promising anti-malaria drug target. PfClpB1 contains all characteristic AAA+ sequence motifs, but the middle domain of PfClpB1 includes a 52-residue long non-conserved insert. Like in most AAA+ ATPases, ATP induces self-association of PfClpB1 into hexamers. PfClpB1 catalyzes the hydrolysis of ATP and its ATPase activity is activated in the presence of casein and poly-lysine. Similar to Escherichia coli ClpB, PfClpB1 reactivates aggregated firefly luciferase, but the PfClpB1-mediated aggregate reactivation is inhibited in the presence of E. coli DnaK, DnaJ, and GrpE. The lack of effective cooperation between PfClpB1 and the bacterial DnaK system may arise from the Plasmodium-specific sequence of the ClpB middle domain. Our results indicate that the chaperone activity of PfClpB1 may support survival of Plasmodium falciparum by maintaining the folding status and activity of apicoplast proteins.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Ngansop
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Anna
authors.initials: A
authors.lastname: Zolkiewska
authors.forename: Michal
authors.initials: M
authors.lastname: Zolkiewski
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D048888:Fireflies / Q000201:enzymology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D049409:Luciferases, Firefly / Q000378:metabolism; D016778:Malaria, Falciparum / Q000469:parasitology*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D055503:Protein Multimerization; D020539:Sequence Analysis, Protein
chemical_list: D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D020033:Protein Isoforms; D000255:Adenosine Triphosphate; D049409:Luciferases, Firefly; D000251:Adenosine Triphosphatases
keywords: ATPγS; Apicoplast; ClpB; IPTG; Malaria; Molecular chaperone; Plasmodium falciparum; Protein aggregation; adenosine-5′-(γ-thio)-triphosphate; isopropyl β-d-1-thiogalactopyranoside