# Mechanism of the Eukaryotic Chaperonin TRiC/CCT

> **NIH NIH R01** · STANFORD UNIVERSITY · 2023 · $140,794

## Abstract

ABSTRACT
Protein folding in the cell is critically dependent on the assistance of molecular chaperones. The ring-shaped
chaperonins are essential members of the cellular folding machinery. These large protein complexes consist of
two stacked seven- to nine-membered rings. Chaperonins bind unfolded substrates in their central cavity and
use binding and hydrolysis of ATP to mediate polypeptide folding. Substrate proteins are thought to fold upon
encapsulation in the central cavity formed by each ring. The long term goal of this program is to understand
how the chaperonin of eukaryotic cells, TRiC, mediates polypeptide folding., TRiC is hetero-oligomeric and
uses ATP cycling to open and close a built-in lid over the central chamber. Intriguingly, TRiC has the ability to
fold some eukaryotic proteins, such as actin, that cannot be folded by any other chaperone. Despite its essential
role in cellular folding, little is known about the mechanism and substrate binding properties of TRiC.
Our work in the previous funding period provided important mechanistic and structural insights into this
chaperonin. We established that the conformational cycle of TRiC is significantly different from that of
bacterial chaperonins and demonstrated subunit diversity confers dramatic functional asymmetry to this
seemingly symmetric chaperonin. Importantly, in the previous funding period we developed a recombinant
system to study this chaperonin that for the first time makes it possible to generating mutants that can be
studies functionally and structurally. These breakthroughs enable us to study how TRiC facilitates folding in
unprecedented detail, through the following proposed aims:
1. Characterize of the nucleotide cycle of the chaperonin TRiC: Chaperonins use ATPase cycling to
promote conformational changes leading to protein folding. We want to understand how the ATPase cycle of
TRiC is coordinated among the different TRiC subunits, and how ATP cycling drives conformational changes
in the chaperonin and how the "built-in" lid that opens and closes in response to ATP-binding and hydrolysis.
2. Define the molecular basis of TRiC-substrate interactions: Little is known about the molecular basis of
TRiC-substrate interactions. We want to define the substrate recognition code of the binding sites for the
different subunits in the chaperonin and define the motifs within substrates that are recognized by TRiC.
3. Investigate the mechanism of TRiC-assisted substrate folding: The exact role that chaperonins play with
respect to the substrate is still a mystery. We will explore the effect of TRiC on substrate proteins during the
different stages of the folding cycle by combining biochemical approaches together with crosslinking and
fluorescence spectroscopy.
Importantly, recent observations have highlighted the links between TRiC and several pathological states
incuding cancer, viral infection and neurodegeneration. Thus our project deciphering the mechanism of this
chaperoni...

## Key facts

- **NIH application ID:** 10725077
- **Project number:** 3R01GM074074-15S1
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Judith Frydman
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $140,794
- **Award type:** 3
- **Project period:** 2005-04-01 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10725077

## Citation

> US National Institutes of Health, RePORTER application 10725077, Mechanism of the Eukaryotic Chaperonin TRiC/CCT (3R01GM074074-15S1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10725077. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*