This is the fourth TRXL(thioredoxin-like) domain found in UDP-glucose:glycoprotein glucosyltransferase (UGGT)[1].

1: Interdomain conformational flexibility underpins the activity of UGGT, the eukaryotic glycoprotein secretion checkpoint. Roversi P, Marti L, Caputo AT, Alonzi DS, Hill JC, Dent KC, Kumar A, Levasseur MD, Lia A, Waksman T, Basu S, Soto Albrecht Y, Qian K, McIvor JP, Lipp CB, Siliqi D, Vasiljevic S, Mohammed S, Lukacik P, Walsh MA, Santino A, Zitzmann N; Proc Natl Acad Sci U S A. 2017;114:8544-8549. PMID:28739903