3,4 ✉ mHsp60-mHsp10 assists the folding of mitochondrial matrix proteins without the negative ATP binding inter-ring cooperativity of GroEL-GroES. Here we report the crystal structure of an ATP (ADP:BeF 3 -bound) ground-state mimic double-ring mHsp60 14 -(mHsp10 7 ) 2 football complex, and the cryo-EM structures of the ADP-bound successor mHsp60 14 -(mHsp10 7 ) 2 complex, and a single-ring mHsp60 7 -mHsp10 7 half-football. The structures explain the nucleotide dependence of mHsp60 ring formation, and reveal an inter-ring nucleotide symmetry consistent with the absence of negative cooperativity. In the ground-state a two-fold symmetric H-bond and a salt bridge stitch the double-rings together, whereas only the H-bond remains as the equatorial gap increases in an ADP football poised to split into halffootballs. Refolding assays demonstrate obligate single-and double-ring mHsp60 variants are active, and complementation analysis in bacteria shows the single-ring variant is as efficient as wild-type mHsp60. Our work provides a structural basis for active single-and double-ring complexes coexisting in the mHsp60-mHsp10 chaperonin reaction cycle.
The GroEL–GroES chaperonin system is probably one of the most studied chaperone systems at the level of the molecular mechanism. Since the first reports of a bacterial gene involved in phage morphogenesis in 1972, these proteins have stimulated intensive research for over 40 years. During this time, detailed structural and functional studies have yielded constantly evolving concepts of the chaperonin mechanism of action. Despite of almost three decades of research on this oligomeric protein, certain aspects of its function remain controversial. In this review, we highlight one central aspect of its function, namely, the active intermediates of its reaction cycle, and present how research to this day continues to change our understanding of chaperonin-mediated protein folding.
Most protein molecules are dynamic and marginally stable and therefore constantly at risk for acquiring misfolded conformations. Constant surveillance is required to preserve proteostasis. Maintenance of the mitochondrial proteome relies on a diverse set of molecular chaperones and proteases, which together form an interconnected network. An imbalance in mitochondrial proteostasis will result in the accumulation of damaged polypeptides, potentially leading to collapse of mitochondrial integrity. The Hsp60 and Hsp70 chaperone systems play a central role in the folding of matrix‐localised proteins. In this article, we summarise major aspects of the molecular function of these nano‐machines and their interplay with other matrix chaperones and proteases. Key Concepts Hsp60 and Hsp70 chaperone systems play a crucial role in the maintenance of mitochondrial proteostasis. Hsp60 and Hsp70 carry out various functions via interaction with a large number of extra‐mitochondrial complexes. In addition to its critical role in protein import into the mitochondria, Hsp70 plays an important role in protein folding, disaggregation and degradation in the mitochondrial matrix. Hsp60 is an essential protein that plays a central role in protein‐folding within the mitochondrial matrix. The Hsp60 reaction cycle differs from that of GroEL in its incorporation of a single‐ring intermediate in the reaction cycle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.