title: Conformational changes of plasma fibronectin detected upon adsorption to solid substrates: a spin-label study.
abstract: Changes in local environment of the free sulfhydryl groups in plasma fibronectin upon adsorption of the protein to polystyrene beads have been examined by electron spin resonance (ESR) spin-label spectroscopy. The two free sulfhydryl groups per subunit of plasma fibronectin were modified chemically with an [15N, 2H]maleimide spin-label. For soluble fibronectin, both free sulfhydryl groups are shown to be in confined environments as evidenced from the labeled protein exhibiting a strongly immobilized ESR spectrum as described previously using [14N, 1H]maleimide spin-labels [Lai, C.-S., & Tooney, N. M. (1984) Arch. Biochem. Biophys. 228, 465-473]. When the labeled protein was adsorbed to the beads, half of the strongly immobilized component was found to convert into a weakly immobilized component, a result indicating that one of the two labeled sites becomes exposed and exhibit a fast tumbling motion. Experiments conducted using various spin-labeled fibronectin fragments suggest that the newly exposed labeled site is located between the DNA-binding and the cell-binding regions of the molecule. The data obtained indicate that, upon adsorption to polystyrene beads, plasma fibronectin undergoes a conformational change through which the buried free sulfhydryl group near the cell-binding region of the molecule is exposed. This observation may have important implications regarding the expression of cell adhesive properties of the fibronectin molecule.
authors.affiliation: Department of Radiology, National Biomedical ESR Center, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: C
authors.initials: C
authors.lastname: Narasimhan
authors.forename: C S
authors.initials: CS
authors.lastname: Lai
mesh_terms: D000327:Adsorption; D004578:Electron Spin Resonance Spectroscopy; D005353:Fibronectins / Q000097:blood*; D011137:Polystyrenes; D011487:Protein Conformation; D013113:Spin Labels; D013438:Sulfhydryl Compounds / Q000097:blood*
chemical_list: D005353:Fibronectins; D011137:Polystyrenes; D013113:Spin Labels; D013438:Sulfhydryl Compounds