4A0O: Symmetry-free Cryo-em Map Of Tric In The Nucleotide-free (apo) State

The eukaryotic group II chaperonin TRiC/CCT is a 16-subunit complex with eight distinct but similar subunits arranged in two stacked rings. Substrate folding inside the central chamber is triggered by ATP hydrolysis. We present five cryo-EM structures of TRiC in apo and nucleotide-induced states without imposing symmetry during the 3D reconstruction. These structures reveal the intra- and inter-ring subunit interaction pattern changes during the ATPase cycle. In the apo state, the subunit arrangement in each ring is highly asymmetric, whereas all nucleotide-containing states tend to be more symmetrical. We identify and structurally characterize an one-ring closed intermediate induced by ATP hydrolysis wherein the closed TRiC ring exhibits an observable chamber expansion. This likely represents the physiological substrate folding state. Our structural results suggest mechanisms for inter-ring-negative cooperativity, intra-ring-positive cooperativity, and protein-folding chamber closure of TRiC. Intriguingly, these mechanisms are different from other group I and II chaperonins despite their similar architecture.
PDB ID: 4A0ODownload
MMDB ID: 97325
PDB Deposition Date: 2011/9/10
Updated in MMDB: 2017/04
Experimental Method:
electron microscopy
Resolution: 10.5  Å
Source Organism:
Similar Structures:
Biological Unit for 4A0O: hexadecameric; determined by author
Molecular Components in 4A0O
Label Count Molecule
Proteins (16 molecules)
T-complex Protein 1 Subunit Beta(Gene symbol: CCT2)
Molecule annotation
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Citing MMDB