Conformational change of chaperone Hsc70 upon binding to a decapeptide: A circular dichroism study

Abstract

The conformation of bovine Hsc70, a 70‐kDa heat shock cognate protein, and its conformational change upon binding to decapeptides, was studied by CD spectroscopy and secondary structure prediction (Chou, P.Y. & Fasman, G.D., 1974, Biochemistry 13, 222–245). The CD spectra were analyzed by the LINCOMB method, as well as by the convex constraint analysis (CCA) method (Perczel, A., Park, K., & Fasman, G.D., 1992, Anal. Biochem. 203, 83–93). The result of the CD analysis of Hsc70 (15% α‐helix, 24% β‐sheet, 24% β‐turn, and 38% remainder) was very similar to the predicted secondary structure for the β‐sheet (24%) and the β‐turn (29%). However, there is disagreement between the α‐helical content by CD analysis (15%) and the predicted structure (30%). In spite of the fact that the decapeptides contained a considerable amount of β‐sheet (22%), the interaction of the heat shock protein with the peptide resulted in an overall decrease in the content of β‐sheet conformation (–15%) of the complex. This may be due to induction of a molten globule state. The result of the CCA analysis indicated that the Hsc70 undergoes a conformational change upon binding the decapeptides.