Heat shock protein 90 from Escherichia coli collaborates with the DnaK chaperone system in client protein remodeling

Abstract

Molecular chaperones are proteins that assist the folding, unfolding, and remodeling of other proteins. In eukaryotes, heat shock protein 90 (Hsp90) proteins are essential ATP-dependent molecular chaperones that remodel and activate hundreds of client proteins with the assistance of cochaperones. In Escherichia coli, the activity of the Hsp90 homolog, HtpG, has remained elusive. To explore the mechanism of action of E. coli Hsp90, we used in vitro protein reactivation assays. We found that E. coli Hsp90 promotes reactivation of heat-inactivated luciferase in a reaction that requires the prokaryotic Hsp70 chaperone system, known as the DnaK system. An Hsp90 ATPase inhibitor, geldanamycin, inhibits luciferase reactivation demonstrating the importance of the ATP-dependent chaperone activity of E. coli Hsp90 during client protein remodeling. Reactivation also depends upon the ATP-dependent chaperone activity of the DnaK system. Our results suggest that the DnaK system acts first on the client protein, and then E. coli Hsp90 and the DnaK system collaborate synergistically to complete remodeling of the client protein. Results indicate that E. coli Hsp90 and DnaK interact in vivo and in vitro, providing additional evidence to suggest that E. coli Hsp90 and the DnaK system function together.

Deciphering the Magainin Resistance Process of Escherichia coli Strains in Light of the Cytosolic Proteome

“…Another upregulated protein is commonly reported as a stress response, namely, a heat shock protein (spot 335). Heat shock protein 90 (YP_001726093.1) participates in several cellular process, with protein folding and degradation being its chaperone roles (26). Proteins with other biological functions were also found to be differentially expressed (Fig.…”

Physical Interaction between Bacterial Heat Shock Protein (Hsp) 90 and Hsp70 Chaperones Mediates Their Cooperative Action to Refold Denatured Proteins

“…7A, the cyanobacterial DnaJ2 is homologous to the E. coli type II J-protein CbpA. It has been shown that CbpA is particularly effective in making DnaK function with HtpG (20). Thus, the type II J-protein may play a special role for the cooperative action of HtpG with DnaK.…”

“…The DnaK system consists of DnaK, GrpE, and DnaJ or CbpA. Their results suggest that the DnaK chaperone system acts first on the substrate protein, and then HtpG and the DnaK system function collaboratively to complete remodeling of the substrate (20).…”

“…We tested by inhibiting the ATPase activity of HtpG with radicicol whether ATP is essential for the enhancement of the DnaK2-assisted refolding by HtpG. The collaboration of the E. coli HtpG with the DnaK chaperone system in the assistance of refolding of heat-denatured luciferase and G6PDH depends on ATP (20). Radicicol inhibited this enhancement by HtpG, indicating that the collaboration of HtpG with the DnaK2/DnaJ2/GrpE chaperone system depended on ATP.…”

Bacterial Inclusion Bodies: Discovering Their Better Half

“…On the other hand there is no doubt that protein disaggregation is an ATP-driven process [20]. For example, HtpG can interact with DnaK/DnaJ/GrpE to further promote refolding of aggregated proteins in an ATP-dependent manner [21]. Alternatively, ClpB can also assist in cooperation with DnaK/DnaJ/GrpE in ATP-driven refolding of aggregated proteins [20,22,23].…”