EUKARYOTIC CYTOSOLIC CHAPERONIN CONTAINS T-COMPLEX POLYPEPTIDE-1 AND 7 RELATED SUBUNITS

We have characterized the cytosolic chaperonin from both rabbit reticu locyte lysate and bovine testis. The heteromeric complex contains eigh t subunits. Partial amino acid sequence data reveal that one of these is t-complex polypeptide 1 (TCP-1), while the other seven are TCP-1-re lated polypeptides, implicating the existence of a multigene family of TCP-1 homologues. We provide evidence that TCP-1 ring complex from bo vine testis can facilitate the folding of both actin and tubulin, alth ough, as in the case of chaperonin from reticulocyte lysate, two cofac tors are required for the generation of properly folded tubulin. An ad ditional molecule of TCP-1 may associate with the chaperonin depending on the purification procedure used. We propose that a highly conserve d region in these polypeptides and in other chaperonins of the cpn60 c haperone family participates in ATP binding.