Tubulin-folding protein; involved in the final step of the tubulin folding pathway. Supercomplex made of cofactors A to E. Cofactors A and D function by capturing and stabilizing tubulin in a quasi-native conformation. Cofactor E binds to the cofactor D-tubulin complex; interaction with cofactor C then causes the release of tubulin polypeptides that are committed to the native state. Detected predominantly in the photoreceptor connecting cilium. Expressed in the retina. Expressed in the rod and cone photoreceptors, extending from the inner segments (IS), through the outer nuclear layer (ONL) and into the synapses in the outer plexiform layer (OPL). Strongly expressed to the photoreceptor connecting cilium at the tips of the IS (at protein level). Belongs to the TBCC family.