Deciphering the mechanism and function of Hsp100 unfoldases from protein structure

Authors

Grace Lee
Rebecca S Kim
Sang Bum Lee
Sukyeong Lee
Francis T F Tsai

Publication Date

12-16-2022

Journal

Biochemical Society Transactions

DOI

10.1042/BST20220590

PMID

36454589

PMCID

PMC9784670

PubMedCentral® Posted Date

12-16-2023

PubMedCentral® Full Text Version

Author MSS

Published Open-Access

yes

Keywords

Escherichia coli Proteins, Substrate Specificity, Molecular Chaperones, Heat-Shock Proteins, Peptides, Adenosine Triphosphate, Hsp100, Clp, chaperone, ATPase, unfoldase, disaggregase, protease

Abstract

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.