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Trigger factor associates with GroEL in vivo and promotes its binding to certain polypeptides
O Kandror1, M Sherman, R Moerschell
1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
The Journal of Biological Chemistry
|January 17, 1997
Summary
Trigger factor (TF) enhances the protein binding capacity of GroEL, a key molecular chaperone. This TF-GroEL interaction is independent of GroEL phosphorylation and may aid in protein folding.
Area of Science:
- Molecular biology
- Protein biochemistry
Background:
- Trigger factor (TF) is a putative molecular chaperone.
- TF collaborates with GroEL in the degradation of the fusion protein CRAG.
Purpose of the Study:
- To investigate the effect of TF on GroEL's binding affinity for denatured proteins.
- To determine if TF and GroEL phosphorylation are independent regulators of GroEL function.
Main Methods:
- Affinity chromatography using denatured protein columns (fetuin).
- Analysis of TF and GroEL complex formation with and without ATP and GroES.
- Comparison of binding capacities between TF-overproducing cells, TF-deficient cells, and pure GroEL.
Main Results:
- TF enhances GroEL's ability to bind various denatured proteins.
- TF and GroEL form stable complexes, with TF increasing GroEL's binding capacity.
- TF and GroEL phosphorylation are independent regulators of GroEL's interaction with denatured polypeptides.
Conclusions:
- TF association with GroEL significantly enhances its affinity for unfolded proteins.
- TF's prolyl isomerase activity and association with nascent polypeptides suggest a role in protein folding.
- TF and GroEL phosphorylation represent distinct regulatory mechanisms for GroEL function.