Synechocystis hsp17 is an amphitropic protein that stabilizes heat-stressed membranes and binds denatured proteins for subsequent chaperone-mediated refolding

Zsolt Török, Pierre Goloubinoff, Ibolya Horváth, Nelly M. Tsvetkova, Attila Glatz, Gábor Balogh, Viktória Varvasovszki, Dmitry A. Los, Elizabeth Vierling, John H. Crowe, László Vígh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

239 Scopus citations

Abstract

The small heat shock proteins (sHSPs) are ubiquitous stress proteins proposed to act as molecular chaperones to prevent irreversible protein denaturation. We characterized the chaperone activity of Synechocystis HSP17 and found that it has not only protein-protective activity, but also a previously unrecognized ability to stabilize lipid membranes. Like other sHSPs, recombinant Synechocystis HSP17 formed stable complexes with denatured malate dehydrogenase and served as a reservoir for the unfolded substrate, transferring it to the DnaK/DnaJ/GrpE and GroEL/ES chaperone network for subsequent refolding. Large unilamellar vesicles made of synthetic and cyanobacterial lipids were found to modulate this refolding process. Investigation of HSP17-lipid interactions revealed a preference for the liquid crystalline phase and resulted in an elevated physical order in model lipid membranes. Direct evidence for the participation of HSP17 in the control of thylakoid membrane physical state in vivo was gained by examining an hsp17- deletion mutant compared with the isogenic wild-type hsp17+ revertant Synechocystis cells. We suggest that, together with GroEL, HSP17 behaves as an amphitropic protein and plays a dual role. Depending on its membrane or cytosolic location, it may function as a "membrane stabilizing factor" as well as a member of a multichaperone protein-folding network. Membrane association of sHSPs could antagonize the heat-induced hyperfluidization of specific membrane domains and thereby serve to preserve structural and functional integrity of biomembranes.

Original languageEnglish
Pages (from-to)3098-3103
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume98
Issue number6
DOIs
StatePublished - 13 Mar 2001

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