Thioredoxin Domain Containing Protein 9 (TXNDC9)

PHLP3, encodes a 226-amino acid protein with a helical N terminus, a central thioredoxin (TXN) domain, and an acidic C terminus.

Mutation analysis revealed that both the N- and C-terminal domains of PHLP3 were required for the interaction. PHLP3 formed a ternary complex with CCT and either denatured actin or tubulin and inhibited their folding. PHLP3 did not compete with the denatured substrates and had no effect on the basal ATPase activity of CCT, but it slowed the ATPase activity of CCT in the presence of substrates. In vivo, the yeast PHLP3 homolog appeared to coordinate the proper biogenesis of actin and tubulin with prefoldin, a chaperone that facilitates CCT-mediated actin and tubulin folding.