The acidic C-terminal domain of protein disulfide isomerase is not critical for the enzyme subunit function or for the chaperone or disulfide isomerase activities of the polypeptide

• Published in: The EMBO journal Vol. 18; no. 1; pp. 65 - 74
• Main Authors: Koivunen, Peppi, Pirneskoski, Annamari, Karvonen, Päivi, Ljung, Johanna, Helaakoski, Tarja, Notbohm, Holger, Kivirikko, Kari I.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 04-01-1999; Blackwell Publishing Ltd
• Subjects: Amino Acid Sequence; Animals; Caenorhabditis elegans - enzymology; Caenorhabditis elegans - genetics; Catalytic Domain - genetics; chaperone; Circular Dichroism; collagen; Dimerization; Escherichia coli - genetics; Humans; In Vitro Techniques; Medicin och hälsovetenskap; microsomal triglyceride transfer protein; Molecular Chaperones - chemistry; Molecular Chaperones - genetics; Molecular Chaperones - metabolism; Molecular Sequence Data; Mutation; Nucleopolyhedrovirus - genetics; Peptides; Point Mutation; prolyl 4-hydroxylase; Protein Conformation; protein disulfide isomerase; Protein Disulfide-Isomerases - chemistry; Protein Disulfide-Isomerases - genetics; Protein Disulfide-Isomerases - metabolism; Protein Structure, Secondary; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Sequence Deletion; Spodoptera
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/18.1.65

Protein disulfide isomerase (PDI) is a multifunctional polypeptide that acts as a subunit in the animal prolyl 4‐hydroxylases and the microsomal triglyceride transfer protein, and as a chaperone that binds various peptides and assists their folding. We report here that deletion of PDI sequences corresponding to the entire C‐terminal domain c, previously thought to be critical for chaperone activity, had no inhibitory effect on the assembly of recombinant prolyl 4‐hydroxylase in insect cells or on the in vitro chaperone activity or disulfide isomerase activity of purified PDI. However, partially overlapping critical regions for all these functions were identified at the C‐terminal end of the preceding thioredoxin‐like domain a′. Point mutations introduced into this region identified several residues as critical for prolyl 4‐hydroxylase assembly. Circular dichroism spectra of three mutants suggested that two of these mutations may have caused only local alterations, whereas one of them may have led to more extensive structural changes. The critical region identified here corresponds to the C‐terminal α helix of domain a′, but this is not the only critical region for any of these functions.