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Biochemical characterization of the apicoplast-targeted AAA+ ATPase ClpB from Plasmodium falciparum
Fabrice Ngansop1, Hui Li, Anna Zolkiewska
1Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.
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.
Insights
The malaria parasite Plasmodium falciparum has a protein, PfClpB1, that helps maintain essential proteins. This chaperone protein
Area of Science:
- Molecular biology
- Protein biochemistry
- Parasitology
Background:
- ClpB proteins are molecular chaperones essential for reactivating aggregated proteins.
- ClpB is crucial for the survival and infectivity of many pathogenic microorganisms.
- Studies on ClpB in pathogens are limited, especially in the malaria parasite Plasmodium falciparum.
Purpose of the Study:
- To purify and characterize PfClpB1, an isoform of ClpB from Plasmodium falciparum.
- To investigate the function and properties of PfClpB1, a potential drug target.
- To understand the role of PfClpB1 in the apicoplast of Plasmodium falciparum.
Main Methods:
- Purification and characterization of PfClpB1.
- Analysis of PfClpB1's ATPase activity and self-association.
- Testing PfClpB1's ability to reactivate aggregated proteins.
- Investigating the interaction of PfClpB1 with bacterial chaperone systems.
Main Results:
- PfClpB1 was purified and found to contain characteristic AAA+ motifs with a unique insert.
- PfClpB1 forms hexamers upon ATP binding and exhibits ATPase activity.
- PfClpB1 can reactivate aggregated firefly luciferase.
- PfClpB1's chaperone activity is inhibited by the bacterial DnaK chaperone system.
Conclusions:
- PfClpB1 is a functional molecular chaperone targeted to the apicoplast, an essential organelle in Plasmodium falciparum.
- The unique structure of PfClpB1 may explain its limited cooperation with bacterial chaperones.
- PfClpB1 likely plays a vital role in maintaining protein homeostasis within the apicoplast, supporting parasite survival.
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