# Structure and function of mitochondrial Hsp60

> **NIH NIH F31** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2021 · $38,612

## Abstract

PROJECT SUMMARY/ABSTRACT
The mitochondrial heat shock protein (Hsp) 60 molecular chaperone is critical in proteostasis and stress
response, catalyzing ATP hydrolysis-dependent folding of mitochondrial proteins. While the precise folding
mechanism is unknown, Hsp60 is proposed to function like the bacterial ortholog GroEL in which unfolded `client'
proteins are enclosed in its central chamber, formed in part by its co-chaperone Hsp10, allowing them to fold
without interference from other cellular components. Mutations in Hsp60 cause severe neurodegenerative
diseases termed hereditary spastic paraplegias, and Hsp60 expression is upregulated in a subset of cancers,
making this chaperone a significant therapeutic target. However, high-resolution structural information on Hsp60
is limited, leaving unresolved critical questions about oligomer organization, allosteric regulation, and interactions
with client proteins throughout its reaction cycle. The objective of this proposal is to determine the mechanism
of Hsp60 function using an integrated structural and chemical biology approach. Herein, I propose to solve high-
resolution cryo-electron microscopy (cryo-EM) structures of Hsp60-client complexes at different nucleotide-
bound and oligomeric states, in order to identify client interaction surfaces important for Hsp60-assisted protein
folding (SA1). In exciting preliminary data, I have generated high-resolution (2.5 Å) cryo-EM structures of the
ATP-bound Hsp60-Hsp10 double ring complex. This structure reveals novel inter-ring arrangements, indicating
a distinct chaperonin mechanism of action and providing an excellent basis for the proposed studies. To
complement these studies, I will also investigate the effects of disease-causing mutations and small molecule
inhibitors on Hsp60 structure and function, in order to identify elements critical for Hsp60 function, and determine
how this complex macromolecular machine can be perturbed (SA2). This will be accomplished by using
biochemical and biophysical assays, as well as by solving cryo-EM structures of inhibitor-bound and mutant
Hsp60 complexes. These studies will dramatically increase understanding of Hsp60 mechanism, as well as
contribute to the development of the first well-validated Hsp60 chemical probes. This work, and my concomitant
development as a structural and chemical biologist, will be enabled by a unique training environment formed by
the labs of Dan Southworth and Jason Gestwicki, experts in studying molecular chaperones using cryo-EM and
chemical biology, respectively.

## Key facts

- **NIH application ID:** 10236100
- **Project number:** 1F31GM142279-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Julian Braxton
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $38,612
- **Award type:** 1
- **Project period:** 2021-06-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10236100

## Citation

> US National Institutes of Health, RePORTER application 10236100, Structure and function of mitochondrial Hsp60 (1F31GM142279-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10236100. Licensed CC0.

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