The Brichos domain of prosurfactant protein C can hold and fold a transmembrane segment

Protein Sci. 2009 Jun;18(6):1175-82. doi: 10.1002/pro.123.


Prosurfactant protein C (proSP-C) is a 197-residue integral membrane protein, in which the C-terminal domain (CTC, positions 59-197) is localized in the endoplasmic reticulum (ER) lumen and contains a Brichos domain (positions 94-197). Mature SP-C corresponds largely to the transmembrane (TM) region of proSP-C. CTC binds to SP-C, provided that it is in nonhelical conformation, and can prevent formation of intracellular amyloid-like inclusions of proSP-C that harbor mutations linked to interstitial lung disease (ILD). Herein it is shown that expression of proSP-C (1-58), that is, the N-terminal propeptide and the TM region, in HEK293 cells results in virtually no detectable protein, while coexpression of CTC in trans yields SDS-soluble monomeric proSP-C (1-58). Recombinant human (rh) CTC binds to cellulose-bound peptides derived from the nonpolar TM region, but not the polar cytosolic part, of proSP-C, and requires >/=5-residues for maximal binding. Binding of rhCTC to a nonhelical peptide derived from SP-C results in alpha-helix formation provided that it contains a long TM segment. Finally, rhCTC and rhCTC Brichos domain shows very similar substrate specificities, but rhCTC(L188Q), a mutation linked to ILD is unable to bind all peptides analyzed. These data indicate that the Brichos domain of proSP-C is a chaperone that induces alpha-helix formation of an aggregation-prone TM region.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cell Membrane / chemistry
  • Circular Dichroism
  • Humans
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Pulmonary Surfactant-Associated Protein C / chemistry*
  • Pulmonary Surfactant-Associated Protein C / genetics
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics


  • Pulmonary Surfactant-Associated Protein C
  • Recombinant Proteins
  • SFTPC protein, human