title: The foldase CYPB is a component of the secretory pathway of Aspergillus niger and contains the endoplasmic reticulum retention signal HEEL.
abstract: Here we report the isolation and characterization of the cypB gene from Aspergillus niger. The cypB gene encodes a protein with a predicted molecular weight of 20.7 kDa, which shows a high degree of identity to the cyclophilin family of peptidyl prolyl cis-trans isomerases (PPIases) from other eukaryotes. The 5' untranslated region of cypB includes three sequences resembling UPREs (unfolded protein response elements). The expression of cypB is upregulated by tunicamycin and DTT, suggesting that at least one UPRE is functional. The CYPB protein also has a 23-amino acid sequence which serves to target the protein to the endoplasmic reticulum (ER), and the ER retention sequence HEEL. CYPB-(His)(6) was expressed in Escherichia coli; the purified protein is capable of isomerizing a substrate peptide in vitro. This is also the first report to show that C-terminal addition of the sequence HEEL is sufficient to ensure retention of the green fluorescent protein (GFP) within the ER.
authors.affiliation: Danisco Cultor Innovation Copenhagen, Langebrogade 1, 1001 Copenhagen, Denmark. g7pmd@danisco.com
authors.forename: P M
authors.initials: PM
authors.lastname: Derkx
authors.forename: S M
authors.initials: SM
authors.lastname: Madrid
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology / Q000235:genetics*; D003001:Cloning, Molecular; D021983:Cyclophilins / Q000235:genetics* / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D007536:Isomerism; D009842:Oligopeptides / Q000378:metabolism; D019696:Peptidylprolyl Isomerase; D021382:Protein Sorting Signals / Q000235:genetics*; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA
chemical_list: D005656:Fungal Proteins; D009842:Oligopeptides; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; C081786:cyclophilin B; D021983:Cyclophilins; D019696:Peptidylprolyl Isomerase