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PDIb family, ERp57 subfamily, first redox inactive TRX-like domain b; ERp57 (or ERp60) exhibits both disulfide oxidase and reductase functions like PDI, by catalyzing the formation of disulfide bonds of newly synthesized polypeptides in the ER and acting as isomerases to correct any non-native disulfide bonds. It also displays chaperone activity to prevent protein aggregation and facilitate the folding of newly synthesized proteins. ERp57 contains two redox-active TRX (a) domains and two redox inactive TRX-like (b) domains. It shares the same domain arrangement of abb'a' as PDI, but lacks the C-terminal acid-rich region (c domain) that is present in PDI. ERp57 interacts with the lectin chaperones, calnexin and calreticulin, and specifically promotes the oxidative folding of glycoproteins. Similar to PDI, the b domain of ERp57 is likely involved in binding to substrates.
Jiyao W et al.(2023). "The conserved domain database in 2023.",