Aims: A recently discovered group of conditionally disordered chaperones share a very unique feature; they need to lose structure to become active as chaperones. This activation mechanism makes these chaperones particularly suited to respond to protein-unfolding stress conditions, such as oxidative unfolding. However, the role of this disorder in stress-related activation, chaperone function, and the crosstalk with other chaperone systems is not yet clear. Here, we focus on one of the members of the conditionally disordered chaperones, a thiol-redox switch of the bacterial proteostasis system, Hsp33. Results: By modifying the Hsp33's sequence, we reveal that the metastable region has evolved to abolish redox-dependent chaperone activity, rather than enhance binding affinity for client proteins. The intrinsically disordered region of Hsp33 serves as an anchor for the reduced, inactive state of Hsp33, and it dramatically affects the crosstalk with the synergetic chaperone system, DnaK/J. Using mass spectrometry, we describe the role that the metastable region plays in determining client specificity during normal and oxidative stress conditions in the cell. Innovation and Conclusion: We uncover a new role of protein plasticity in Hsp33's inactivation, client specificity, crosstalk with the synergistic chaperone system DnaK/J, and oxidative stress-specific interactions in bacteria. Our results also suggest that Hsp33 might serve as a member of the house-keeping proteostasis machinery, tasked with maintaining a "healthy" proteome during normal conditions, and that this function does not depend on the metastable linker region.
Bibliographical noteFunding Information:
The authors are grateful to the German-Israel Foundation (grant number: I-2332-1149.9/2012), Marie-Curie integration grant (project number: 618806), Abish-Frenkel Foundation, Israel Science Foundation (Grant Number: 1765/13), and Human Frontier Science Program (CDA00064/2014) for financial support, and to the Dean Fellowship for funding O.S. A.F. was supported by grants from the Israel Science Foundation (ISF) and the Israel Cancer Research Foundation (ICRF); H.A. was supported by the Dalya and Dan Maydan Fellowship.
© Copyright 2017, Mary Ann Liebert, Inc. 2017.
- ATP-independent chaperone
- intrinsically disordered proteins
- protein thiol switches
- redox-regulated chaperone