Phosphorylation and transformation sensitivity of a major collagen-binding protein of fibroblasts

J Biol Chem. 1986 Jun 5;261(16):7531-6.


Using affinity chromatography with immobilized gelatin and native type I collagen, we have identified the major collagen-binding proteins in Nonidet P-40 extracts of chick embryo fibroblasts labeled with [35S] methionine. After washing the gelatin- or collagen-Sepharose beads with high ionic strength buffer, a 47,000-dalton protein was the only major protein besides fibronectin found to bind to these affinity beads. The isoelectric point of this protein was approximately 9.0, with a closely spaced minor spot. The total amount and the synthesis of this collagen-binding protein were both decreased in Rous sarcoma virus-transformed cells. This collagen-binding protein was found to be phosphorylated by incubating intact cells with [32P]orthophosphate. Phosphoamino acid analysis revealed that serine and threonine residues were phosphorylated, but tyrosine was not. Although quantities of the 47,000-dalton protein labeled with [35S]methionine were decreased by a factor 2.5 after transformation, the incorporation of [32P]orthophosphate/unit of protein was 5-7-fold higher in transformed cells. In temperature-sensitive mutant virus-infected cells, the amount of the 47,000-dalton protein was also decreased at the temperature permissive for transformation, and the incorporation of [32P]orthophosphate/protein was also increased. These studies establish that a major membrane-associated collagen-binding protein of fibroblasts is phosphorylated and that it is altered in both total quantity and degree of phosphorylation after malignant transformation.

MeSH terms

  • Animals
  • Avian Sarcoma Viruses
  • Cell Transformation, Neoplastic / metabolism*
  • Cells, Cultured
  • Chick Embryo
  • Chromatography, Affinity
  • Fibroblasts / analysis
  • Molecular Weight
  • Mutation
  • Phosphorus Radioisotopes
  • Phosphorylation
  • Receptors, Collagen
  • Receptors, Immunologic / isolation & purification
  • Receptors, Immunologic / metabolism*
  • Sulfur Radioisotopes
  • Temperature


  • Phosphorus Radioisotopes
  • Receptors, Collagen
  • Receptors, Immunologic
  • Sulfur Radioisotopes