Protein disulfide isomerase acts as a molecular chaperone during the assembly of procollagen

J Biol Chem. 1998 Apr 17;273(16):9637-43. doi: 10.1074/jbc.273.16.9637.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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

Substances

  • Molecular Chaperones
  • Procollagen
  • Recombinant Proteins
  • Collagen
  • Protein Disulfide-Isomerases