Structural basis for ATP-driven double-ring assembly of the human mitochondrial Hsp60 chaperonin

Tascon, I.; Lopez-Alonso, J. P.; Shkolnisky, Y.; Gil-Carton, D.; Vilchez-Garcia, J.; Berruezo, A. G.; Gomez-Llorente, Y.; Malik, R.; Jebara, F.; Patra, M.; Hirsch, J. A.; Azem, A.; Ubarretxena-Belandia, I.

doi:10.1101/2025.10.04.680452

bioRxiv · 10.1101/2025.10.04.680452

Structural basis for ATP-driven double-ring assembly of the human mitochondrial Hsp60 chaperonin

Tascon, I.·Lopez-Alonso, J. P.·Shkolnisky, Y.·Gil-Carton, D.·Vilchez-Garcia, J.·Berruezo, A. G.·Gomez-Llorente, Y.·Malik, R.·Jebara, F.·Patra, M.·Hirsch, J. A.·Azem, A.·Ubarretxena-Belandia, I.

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Abstract

The ATP-driven mHsp60:mHsp10 chaperonin system assists protein folding within the mitochondrial matrix of human cells. Substrate protein folding has been proposed to occur through interconnected single- and double-ring pathways. In the absence of nucleotide, mHsp60 exists in equilibrium between free protomers and heptameric single rings, while the formation of double rings requires ATP. Here, we present cryo-electron microscopy structures of mHsp60 in the apo state, bound to ATP, and bound to ATP in complex with the cochaperonin mHsp10. ATP binding to single-ring apo mHsp607 triggers coordinated conformational changes in the intermediate and apical domains, resulting in a highly dynamic apical region within the ring. Extensive inter-subunit rearrangements flatten the equatorial surface of each ring, thereby enabling inter-ring contacts that stitch the rings together to form double-ring mHsp6014. Collectively, these structures define the structural basis of ATP-driven double-ring assembly of a human mitochondrial chaperonin responsible for maintaining mitochondrial protein homeostasis.

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Tascon, I., Lopez-Alonso, J. P., Shkolnisky, Y., Gil-Carton, D., Vilchez-Garcia, J., Berruezo, A. G., Gomez-Llorente, Y., Malik, R., Jebara, F., Patra, M., Hirsch, J. A., Azem, A., Ubarretxena-Belandia, I.. 2025-10-05. Structural basis for ATP-driven double-ring assembly of the human mitochondrial Hsp60 chaperonin. https://doi.org/10.1101/2025.10.04.680452

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