Endoplasmic Reticulum Protein 27 (ERP27)

ERP27 is a noncatalytic member of the protein disulfide isomerase (PDI) family of endoplasmic reticulum (ER) proteins.The deduced 273-amino acid protein has an N-terminal signal sequence, an N-glycosylation site, and a putative ER retention signal, but it lacks the CxxC thioredoxin superfamily active site. ERP27 has a 2-domain structure homologous to the noncatalytic b and b-prime domains of PDI. It shares 65.5% amino acid identity with its mouse ortholog. Serial analysis of gene expression (SAGE) showed highest ERP27 expression in pancreas, with lower levels in spleen, lung, kidney, thymus, and bone marrow. Immunofluorescence studies in COS-7 cells localized ERP27 to the ER. Peptide binding assays and NMR spectroscopy revealed changes in ERp27 conformation upon substrate binding.