Thermosome, archaeal (IPR012714)

Short name: Thermosome_arc

Overlapping homologous superfamilies

Family relationships


Members of this eukaryotic family are part of the group II chaperonin complex called CCT (chaperonin containing TCP-1 or Tailless Complex Polypeptide 1) or TRiC [PMID: 1352857, PMID: 15335898]. Chaperonins are involved in productive folding of proteins [PMID: 11340060]. They share a common general morphology, a double toroid of 2 stacked rings. The archaeal equivalent group II chaperonin is often called the thermosome [PMID: 11580264]. Both the thermosome and the TCP-1 family of proteins are weakly, but significantly [PMID: 1352040], related to the cpn60/groEL chaperonin family (see IPR001844).

The TCP-1 protein was first identified in mice where it is especially abundant in testis but present in all cell types. It has since been found and characterised in many other animal species, as well as in yeast, plants and protists. The TCP1 complex has a double-ring structure with central cavities where protein folding takes place [PMID: 20194787]. TCP-1 is a highly conserved protein of about 60 kDa (556 to 560 residues) which participates in a hetero-oligomeric 900 kDa double-torus shaped particle [PMID: 1630492] with 6 to 8 other different, but homologous, subunits [PMID: 7601114]. These subunits, the chaperonin containing TCP-1 (CCT) subunit beta, gamma, delta, epsilon, zeta and eta are evolutionary related to TCP-1 itself [PMID: 7953530, PMID: 7846767]. Non-native proteins are sequestered inside the central cavity and folding is promoted by using energy derived from ATP hydrolysis [PMID: 10753735, PMID: 10550210, PMID: 12354605]. The CCT is known to act as a molecular chaperone for tubulin, actin and probably some other proteins [PMID: 18595008, PMID: 15027029].

Thermosome (or cpn60) is the name given to the archaeal rather than eukaryotic form of the group II chaperonin (counterpart to the group I chaperonin, GroEL/GroES, in bacteria), a toroidal, ATP-dependent molecular chaperone that assists in the folding or refolding of nascent or denatured proteins [PMID: 11580264]. Cpn60 consists of two stacked octameric rings, which are composed of one or two different subunits. Various homologous subunits, one to five per archaeal genome, may be designated alpha, beta, etc., but phylogenetic analysis does not show distinct alpha subunit and beta subunit lineages traceable to ancient paralogs. TF55 from thermophilic bacteria is also included in this entry.

GO terms

Biological Process

GO:0006457 protein folding

Molecular Function

GO:0005524 ATP binding
GO:0051082 unfolded protein binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.