<p> This family represents eukaryotic protein disulphide isomerases retained in the endoplasmic reticulum (ER) and other closely related forms. Some members have been assigned alternative or additional functions such as prolyl 4-hydroxylase anddolichyl-diphosphooligosaccharide-protein glycotransferase. Members of this family have at least two protein-disulphide domains, each similar to thioredoxin but with the redox-active disulphide in the motif PWCGHCK, and an ER retention signal at the extreme C terminus (KDEL, HDEL, and similar motifs).</p>