# Structural and Functional Studies of Hsp70 Molecular Chaperones

> **NIH NIH R01** · VIRGINIA COMMONWEALTH UNIVERSITY · 2020 · $318,263

## Abstract

Project Summary
 As ubiquitous and highly conserved molecular chaperones, Hsp70s play multiple essential roles in
maintaining cellular protein homeostasis (proteostasis) through assisting in protein folding, assembly,
degradation, disaggregation, and transportation across membrane. The fundamental importance of maintaining
proteostasis inevitably links Hsp70s with many life-threatening human diseases, most notably cancers and
neurodegenerative disorders. Thus, elucidating the biochemical and structural properties of Hsp70s will not
only advance our understanding on the basic molecular mechanism of Hsp70-assited folding, but also provide
a crucial and solid foundation for rational design of novel therapeutics for cancers and neurodegenerative
disorders. All Hsp70s contain two functional domains, a nucleotide binding domain (NBD) and a substrate-
binding domain (SBD), corresponding to two key intrinsic biochemical activities: ATPase and polypeptide
substrate binding. Although NBD and SBD can each bind their substrates independently, the chaperone
activity of Hsp70s strictly requires the tight coupling of these two domains upon ATP binding. The current
paradigm for Hsp70 chaperone cycle was proposed primarily based on this essential allosteric coupling, which
is mainly about how different nucleotide-bound states control polypeptide substrate binding. In spite of
extensive efforts, the very basic mechanisms of Hsp70-assisted protein folding are still ill-defined due to a lack
of in-depth understanding of two key questions: 1) Both binding and release of polypeptide substrates were
proposed to occur in the ATP-bound state (Hsp70-ATP). How does Hsp70-ATP decide when to bind and when
to release substrates to promote a productive chaperone cycle? and 2) Until now, no structure is available for
an Hsp70-ATP with a polypeptide substrate bound. How does Hsp70-ATP bind polypeptide substrates to
promote productive protein folding? Thus, the overall objective of this proposal is to analyze these two key
questions in order to dissect the basic molecular mechanisms of Hsp70 chaperone function. Recently, we have
successfully solved three Hsp70-ATP structures and unexpectedly revealed two novel and completely different
conformations of the polypeptide-binding pocket, suggesting that the polypeptide-binding pocket of the ATP-
bound state is highly dynamic. More importantly, our solution studies inspired by these structures have
revolutionized the well-established chaperone cycle with three paradigm-shifting discoveries: 1) an active
release of bound substrate upon ATP-binding, 2) Hsp40 co-chaperone is the key to initiate efficient substrate
binding to Hsp70-ATP and thus start productive chaperone cycle, and 3) an active unfolding by Hsp70’s
polypeptide-binding pocket. Based on these original discoveries, we propose the following two Specific Aims:
1) Characterize the dynamics of Hsp70s’ polypeptide-binding pocket in the active chaperone cycle, and 2)
Determine the ...

## Key facts

- **NIH application ID:** 9913551
- **Project number:** 5R01GM098592-08
- **Recipient organization:** VIRGINIA COMMONWEALTH UNIVERSITY
- **Principal Investigator:** Qinglian Liu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $318,263
- **Award type:** 5
- **Project period:** 2013-09-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9913551

## Citation

> US National Institutes of Health, RePORTER application 9913551, Structural and Functional Studies of Hsp70 Molecular Chaperones (5R01GM098592-08). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9913551. Licensed CC0.

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