analysis of hsp70 chaperone activity using sds page and western blot analyses of transformed e. coli protein

Bewertung der Hsp70-Chaperonaktivität anhand von Escherichia coli dnaK756-Zellen

Heat shock proteins play an important role as molecular chaperones by facilitating protein folding, preventing protein aggregation, and reversing protein misfolding1,2. Heat shock protein 70 (Hsp70) is one of the most prominent molecular chaperones, playing a central role in protein homeostasis3,4. DnaK is the E. coli Hsp70 homologue5.
Various biophysical, biochemical, and cell-based assays have been developed to explore the chaperone activity of Hsp70 and to screen for inhibitors targeting this chaperone6,7,8. Hsp70 is a highly conserved protein. For this reason, several Hsp70s of eukaryotic organisms, such as Plasmodium falciparum (the main agent of malaria), have been reported to substitute for DnaK function in E. coli6,9. In this way, an E. coli-based complementation assay has been developed involving the heterologous expression of Hsp70s in E. coli to explore their cytoprotective function. Typically, this assay involves the utilization of E. coli cells that are either deficient for DnaK or that express a native DnaK that is functionally compromised. While DnaK is not essential for E. coli growth under normal conditions, it becomes essential when the cells are grown under stressful conditions such as elevated temperatures or other forms of stress10,11.
E. coli strains that have been developed to study Hsp70 function using a complementation assay include E. coli dnaK103&#160;(BB2393 [C600 dnaK103(Am) thr::Tn10]) and E. coli dnaK756. E. coli dnaK103&#160;cells produce a truncated DnaK that is non-functional, and as such, the cells grow adequately at 30 &#176;C, while the strain is sensitive to cold and heat stress12,13. Similarly, the E. coli dnaK756/BB2362 (dnaK756&#160;recA::TcR Pdm1,1) strain does not grow above 40 &#176;C14,15. The E. coli dnaK756&#160;strain expresses a mutant native DnaK (DnaK756) characterized by three glycine-to-aspartate substitutions at positions 32, 455, and 468, giving rise to compromised proteostatic outcomes. Consequently, this strain is resistant to bacteriophage &#955; DNA14. Additionally, E. coli&#160;dnaK756 exhibits elevated ATPase activity, while its affinity for the nucleotide exchange factor, GrpE, is reduced16. E. coli DnaK mutant strains serve as ideal models for investigating the chaperone activity of Hsp70 through a complementation approach. Since DnaK is only essential under stressful conditions, the complementation assay is typically conducted at elevated temperatures (Figure 1). Some advantages of using E. coli for this study include its well-characterized genome, rapid growth, and the low cost of culturing and maintenance17.
In this article, we describe in detail a protocol involving the use of E. coli dnaK756&#160;cells to study the function of Hsp70. The Hsp70s we employed in the assay are wild-type DnaK and its chimeric derivative, KPf (made up of the ATPase domain of DnaK fused to the C-terminal substrate-binding domain of Plasmodium falciparum Hsp70-16,18). KPf-V436F was heterologously expressed as a negative control since the mutation essentially blocks it from binding substrates, thus abrogating its chaperone activity9.

Autor im Rampenlicht: Erforschung von Hitzeschockproteinen bei Malaria- und Tuberkuloseinfektionen

Escherichia coli-basierter Komplementationsassay zur Untersuchung der Chaperonfunktion des Hitzeschockproteins 70

I study the role of heat shock proteins in conferring future static protection to antigens that cause human infections such as malaria and tuberculosis. My research essentially focuses on the structure and function features of the heat shock protein machinery of these pathogens that cause human infections. Heatstroke proteins are generally highly concept, however, they display some level of functional specialization.In addition, they are implicated in drug resistant. As such, there are ongoing efforts to target them towards reversing drug resistance in various disease models. They include biochemical, biophysical, bioinformatics, and cell biologic techniques.In other words, various areas of techniques are used to study the roles of these proteins. In our case, the study of proteins of Plasmodium was the main agent of malaria and that they are difficult to produce and this limits the capability to study these proteins. For example, it is difficult to generate sufficient levels to crystallize and image the proteins.We have established some of the functional networks of these proteins in the malaria parasite. We have also established assays to study the compounds targeting these proteins in agents causing malaria and TB.The current protocol is used to explore the chaperone protein folding role and then cytoprotective function of HSP 70 using equal as a model. The protocol could also be adopted for screening small molecule inhibitors targeting protein 70.

Analyse der Hsp70-Chaperon-Aktivität mit SDS PAGE und Western-Blot-Analysen von transformiertem E. coli-Protein

Pipettieren Sie zunächst 80 Mikroliter transformierter E.coli-Zellen in ein Fläschchen. Pipettieren Sie 20 Mikroliter vierfachen Laemmli SDS-Ladepuffer in die Durchstechflasche. Kochen Sie die Suspension 10 Minuten lang bei 100 Grad Celsius in einem Heizblock.Laden Sie dann 10 Mikroliter der Probe auf ein vorgefertigtes SDS-Gel. Elektrophorese des Gels bei Raumtemperatur für eine Stunde bei 120 Volt in SDS-Laufpuffer. Sobald die Elektrophorese abgeschlossen ist, färben Sie das Gel eine Stunde lang in Coomassie-Färbung.Entfärben Sie das Gel in einem Entfärbungspuffer mit 50 % Methanol und 10 % Essigsäure in destilliertem Wasser für zwei Stunden. Legen Sie das Gel in ein Gel-Imaging-System, um die Proteinbanden zu visualisieren. Als nächstes übertragen Sie die Proteine des SDS-Gels auf eine Nitrozellulosemembran.Waschen Sie die Nitrozellulosemembran dreimal in Waschpuffer. Übertragen Sie die Membran auf 5% fettfreie Milch mit Antikörpern, die im Verhältnis eins zu 2.000 verdünnt sind. Inkubieren Sie die Membran mit den Antikörpern bei vier Grad Celsius und schütteln Sie sie eine Stunde lang bei 60 U/min.Waschen Sie anschließend die Nitrozellulosemembran dreimal für jeweils 15 Minuten in TBS-Tween-Puffer, um alle nicht spezifisch gebundenen Antikörper zu entfernen. Übertragen Sie nun die Membran in eine Schale mit dem Sekundärantikörper. Inkubieren Sie die Membran bei vier Grad Celsius und schütteln Sie sie eine Stunde lang bei 60 U/min.Verwenden Sie nach dem Waschen der Membran wie zuvor ein verbessertes Chemilumineszenz-Detektionsreagenz, um die Banden aufzulösen. Visualisieren Sie die Banden mit einem Gel-Imager.

Research

JoVE Journal

Biochemistry

Analysis of Hsp70 Chaperone Activity Using SDS PAGE and Western Blot Analyses of Transformed E. coli Protein

Escherichia coli -Based Complementation Assay to Study the Chaperone Function of Heat Shock Protein 70

Heat shock protein 70 (Hsp70) is a conserved protein that facilitates the folding of other proteins within the cell, making it a molecular chaperone. ...

Forschung

Biochemie

Transformation of E. coli Cells for a Complementation Assay to Assess Hsp70 Chaperone Activity

Transformation von E. coli-Zellen für einen Komplementationsassay zur Beurteilung der Hsp70-Chaperon-Aktivität