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Small heat shock proteins are molecular chaperones

Item Type:Article
Title:Small heat shock proteins are molecular chaperones
Creators Name:Jakob, U. and Gaestel, M. and Engel, K. and Buchner, J.
Abstract:Small heat shock proteins (sHsp) with a molecular mass of 15-30 kDa are ubiquitous and conserved. Up to now their function has remained enigmatic. Increased expression under heat shock conditions and their protective effect on cell viability at elevated temperatures suggest that they may have a function in the formation or maintenance of the native conformation of cytosolic proteins. To test this hypothesis we studied the influence of murine Hsp25, human Hsp27, and bovine alpha-B-crystallin (an eye lens protein homologous to sHsps) on the unfolding and refolding of citrate synthase and alpha-glucosidase in vitro. Here we show that all sHsps investigated act as molecular chaperones in these folding reactions. At stoichiometric amounts they maximally prevent the aggregation of citrate synthase and alpha-glucosidase under heat shock conditions and stabilize the proteins. Furthermore, they promote the functional refolding of these proteins after urea denaturation similar to GroE and Hsp90. The interaction both with unfolding and refolding proteins seems to be ATP-independent.
Keywords:3T3 Cells, Adenosine Triphosphate, Bacterial Proteins, Chaperonin 10, Chaperonin 60, Citrate (si)-Synthase, Crystallins, Enzyme Activation, Heat-Shock Proteins, Hot Temperature, Kinetics, Molecular Weight, Protein Denaturation, Protein Folding, Recombinant Proteins, Urea, alpha-Glucosidases, Animals, Cattle, Mice
Source:Journal of Biological Chemistry
Publisher:American Society for Biochemistry and Molecular Biology
Page Range:1517-1520
Date:25 January 1993
Official Publication:http://www.jbc.org/content/268/3/1517.abstract
PubMed:View item in PubMed

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