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Updated: Jun 4, 2026

Escherichia coli -Based Complementation Assay to Study the Chaperone Function of Heat Shock Protein 70
Published on: March 8, 2024
Subunit arrangement in the dodecameric chloroplast small heat shock protein Hsp21
Wietske Lambert1, Philip J B Koeck, Emma Ahrman
1Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University, Sweden. wietske.lambert@biochemistry.lu.se
Abstract:
Unfolding proteins are prevented from irreversible aggregation by small heat shock proteins (sHsps) through interactions that depend on a dynamic equilibrium between sHsp subunits and sHsp oligomers. A chloroplast-localized sHsp, Hsp21, provides protection to client proteins to increase plant stress resistance. Structural information is lacking concerning the oligomeric conformation of this sHsp. We here present a structure model of Arabidopsis thaliana Hsp21, obtained by homology modeling, single-particle electron microscopy, and lysine-specific chemical crosslinking. The model shows that the Hsp21 subunits are arranged in two hexameric discs, similar to a cytosolic plant sHsp homolog that has been structurally determined after crystallization. However, the two hexameric discs of Hsp21 are rotated by 25° in relation to each other, suggesting a role for global dynamics in dodecamer function.
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