Hsp100 chaperones, also known as Clp proteins, constitute a family of ring-forming ATPases that differ in 3D structure and cellular function from other stress-inducible molecular chaperones. While the vast majority of ATP-dependent molecular chaperones promote the folding of either the nascent chain or a newly imported polypeptide to reach its native conformation, Hsp100 chaperones harness metabolic energy to perform the reverse and facilitate the unfolding of a misfolded polypeptide or protein aggregate. It is now known that inside cells and organelles, different Hsp100 members are involved in rescuing stress-damaged proteins from a previously aggregated state or in recycling polypeptides marked for degradation. Protein degradation is mediated by a barrel-shaped peptidase that physically associates with the Hsp100 hexamer to form a two-component system. Notable examples include the ClpA:ClpP (ClpAP) and ClpX:ClpP (ClpXP) proteases that resemble the ring-forming FtsH and Lon proteases, which unlike ClpAP and ClpXP, feature the ATP-binding and proteolytic domains in a single polypeptide chain. Recent advances in electron cryomicroscopy (cryoEM) together with single-molecule biophysical studies have now provided new mechanistic insight into the structure and function of this remarkable group of macromolecular machines.
Many dietary plants possess high levels of 18-carbon containing lipids from both omega-6 and omega-3 unsaturated fatty acids (e.g., linoleic and alpha-linolenic acid, respectively). These dietary lipids can be metabolized to lipid mediators collectively termed octadecanoids, which can in turn interact with immune cells (e.g., macrophages, eosinophils) to exert a number of potent biological effects. These octadecanoid lipid mediators have been little studied and represent an exciting new area of lipid biochemistry. For further information, see the review in this issue by Quaranta and colleagues (pages 1569–1582). Cover image credit: Emmanuelle Chevallier.
Deciphering the mechanism and function of Hsp100 unfoldases from protein structure
Grace Lee, Rebecca S. Kim, Sang Bum Lee, Sukyeong Lee, Francis T.F. Tsai; Deciphering the mechanism and function of Hsp100 unfoldases from protein structure. Biochem Soc Trans 16 December 2022; 50 (6): 1725–1736. doi: https://doi.org/10.1042/BST20220590
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