This is the N-terminal domain found in Copper resistance protein ScsS present in Proteus mirabilis. ScsC is a powerful disulfide isomerase that is able to refold and reactivate the scrambled disulfide form of the model substrate RNase A. The protein has a thioredoxin 4 domain (Pfam:PF13462) but, unlike other characterized proteins in this family, it is trimeric. The N-terminal domain is responsible for trimerization of ScsC which is needed for isomerase activity [1].

1: A shape-shifting redox foldase contributes to Proteus mirabilis copper resistance. Furlong EJ, Lo AW, Kurth F, Premkumar L, Totsika M, Achard MES, Halili MA, Heras B, Whitten AE, Choudhury HG, Schembri MA, Martin JL; Nat Commun. 2017;8:16065. PMID:28722010