PCYT1B: Proteins and Enzymes

TCP1 beta is a subunit of a cytosolic hetero-oligomer chaperon that is known to be involved in the folding of actin and tubulin. This protein is a member of the chaperonin family, which includes Escherichia coli GroEL, the mitochondrial heat-shock protein Hsp60, the plastid Rubisco-subunit-binding protein and the archaebacterial protein TF55. These chaperonins assist the folding of proteins upon ATP hydrolysis. Nine different subunits of TCP-1 containing chaperonin complexes from mammalian testis and seven different subunits of mouse F9 cells have been identified. It has been suggested that each CCT subunit has a specific, independent function, as they are highly diverged from each other but conserved from mammals to yeast. The expansion in the number of types of CCT subunit, compared with other chaperonins, has allowed CCT to carry out more complex functions that are required for the folding and assembly of highly evolved eukaryotic proteins.