TRiC (complex)

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Structure of Saccharomyces cerevisiae TRiC in the AMP-PNP bound state (PDB 5GW5).[1]

T-complex protein Ring Complex (TRiC), otherwise known as Chaperonin Containing TCP-1 (CCT),[a] is a multiprotein complex and the chaperonin of eukaryotic cells. Like the bacterial GroEL, the TRiC complex aids in the folding of ~10% of the proteome, and actin and tubulin are some of its best known substrates.[2][3] TRiC is an example of a biological machine that folds substrates within the central cavity of its barrel-like assembly using the energy from ATP hydrolysis.

Subunits

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The human TRiC complex is formed by two rings containing 8 similar but non-identical subunits, each with molecular weights of ~60 kDa. The two rings are stacked in an asymmetrical fashion, forming a barrel-like structure with a molecular weight of ~1 MDa.[2][3]

Subunit MW (kDa)[A] Features
TCP1 (CCT1/α) 60
CCT2 (β) 57
CCT3 (γ) 61
CCT4 (δ) 58
CCT5 (ε) 60
CCT6 (ζ) 58 Two copies in human genome, CCT6A and CCT6B.
CCT7 (η) 59
CCT8 (θ) 60

A Molecular weight of human subunits.

Counterclockwise from the exterior, each ring is made of the subunits in the following order: 6-8-7-5-2-4-1-3.[4]

Evolution

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The CCT evolved from the archaeal thermosome ~2Gya, with the two subunits diversifying into multiple units. The CCT changed from having one type of subunit, to having two, three, five, and finally eight types.[4]: fig. 4 

See also

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Notes

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  1. ^ The term "TCP-1" is variously expanded as "T-complex protein 1" and "tailless complex polypeptide 1". The "T-complex" is the same as tailless complex, a CCT locus associated with tail length in mice.

References

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