<p>The TCP-1 protein [<cite idref="PUB00004127"/>, <cite idref="PUB00001019"/>] (Tailless Complex Polypeptide 1) 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. 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 [<cite idref="PUB00004129"/>] with 6 to 8 other different subunits. These subunits, the chaperonin containing TCP-1 (CCT) subunit beta, gamma, delta, epsilon, zeta and eta are evolutionary related to TCP-1 itself [<cite idref="PUB00001034"/>, <cite idref="PUB00005432"/>]. The CCT is known to act as a molecular chaperone for tubulin, actin and probably some other proteins.</p><p>The CCT subunits are highly related to archaebacterial counterparts:</p><ul> <li>TF55 and TF56 [<cite idref="PUB00004112"/>], a molecular chaperone from <taxon tax_id="2286">Sulfolobus shibatae</taxon>. TF55 has ATPase activity, is known to bind unfolded polypeptides and forms a oligomeric complex of two stacked nine-membered rings.</li><li>Thermosome [<cite idref="PUB00000756"/>], from <taxon tax_id="2303">Thermoplasma acidophilum</taxon>. The thermosome is composed of two subunits (alpha and beta) and also seems to be a chaperone with ATPase activity. It forms an oligomeric complex of eight-membered rings.</li> </ul><p>The TCP-1 family of proteins are weakly, but significantly [<cite idref="PUB00004124"/>], related to the cpn60/groEL chaperonin family (see <db_xref db="INTERPRO" dbkey="IPR001844"/>).</p> Chaperonin TCP-1, conserved site