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P5 family, C-terminal redox inactive TRX-like domain; P5 is a protein disulfide isomerase (PDI)-related protein with a domain structure of aa'b (where a and a' are redox active TRX domains and b is a redox inactive TRX-like domain). Like PDI, P5 is located in the endoplasmic reticulum (ER) and displays both isomerase and chaperone activities, which are independent of each other. Compared to PDI, the isomerase and chaperone activities of P5 are lower. The first cysteine in the CXXC motif of both redox active domains in P5 is necessary for isomerase activity. The P5 gene was first isolated as an amplified gene from a hydroxyurea-resistant hamster cell line. The zebrafish P5 homolog has been implicated to play a critical role in establishing left/right asymmetries in the embryonic midline. The C-terminal domain is likely involved in substrate binding, similar to the b and b' domains of PDI.
Jiyao W et al.(2023). "The conserved domain database in 2023.",