Protein disulfide Isomerase Acts as a Molecular Chaperone during the Assembly of Procollagen

• Published in: The Journal of biological chemistry 1998-04, Vol.273 (16), p.9637-9643
• Main Authors: Wilson, R, Lees, J F, Bulleid, N J
• Format: Article
• Language: English
• Subjects: Animals; Binding Sites; Cell Line; Collagen - biosynthesis; Hydroxylation; Molecular Chaperones - metabolism; Polymerase Chain Reaction; Procollagen - biosynthesis; Procollagen - chemistry; Protein Biosynthesis; Protein Denaturation; Protein Disulfide-Isomerases - metabolism; Protein Folding; Protein Processing, Post-Translational; Protein Structure, Secondary; Rabbits; Recombinant Proteins - metabolism; Reticulocytes - metabolism; Spodoptera; Transcription, Genetic; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.16.9637

Protein-disulfide isomerase (PDI) has been shown to be a multifunctional enzyme catalyzing the formation of disulfide bonds, as well as being a component of the enzymes prolyl 4-hydroxylase (P4-H) and microsomal triglyceride transfer protein. It has also been proposed to function as a molecular chaperone during the refolding of denatured proteins in vitro . To investigate the role of this multifunctional protein within a cellular context, we have established a semi-permeabilized cell system that reconstitutes the synthesis, folding, modification, and assembly of procollagen as they would occur in the cell. We demonstrate here that P4-H associates transiently with the triple helical domain during the assembly of procollagen. The release of P4-H from the triple helical domain coincides with assembly into a thermally stable triple helix. However, if triple helix formation is prevented, P4-H remains associated, suggesting a role for this enzyme in preventing aggregation of this domain. We also show that PDI associates independently with the C-propeptide of monomeric procollagen chains prior to trimer formation, indicating a role for this protein in coordinating the assembly of heterotrimeric molecules. This demonstrates that PDI has multiple functions in the folding of the same protein, that is, as a catalyst for disulfide bond formation, as a subunit of P4-H during proline hydroxylation, and independently as a molecular chaperone during chain assembly.