title: One free sulfhydryl group of plasma fibronectin becomes titratable upon binding of the protein to solid substrates.
abstract: The accessibility in human plasma fibronectin of the two free sulfhydryl groups per chain to sulfhydryl reagents 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and a maleimide derivative has been examined. For soluble fibronectin, the free sulfhydryl groups are not accessible to DTNB unless urea or guanidine hydrochloride is added [Smith et al. (1982) J. Biol. Chem. 257, 5831-5838]. Upon binding to polystyrene beads, 0.87 +/- 0.05 sulfhydryl group per chain becomes titratable to DTNB. Experiments using fibronectin fragments demonstrate that this newly exposed sulfhydryl group is located in a Type III homologous unit between the DNA-binding and the cell-binding domains. The results suggest that, upon adsorption to solid substrates, plasma fibronectin undergoes a conformational change, thereby exposing one buried sulfhydryl group. These findings have implications regarding the "surface activation" of adhesion activities of fibronectin.
authors.affiliation: National Biomedical ESR Center, Milwaukee, Wisconsin.
authors.forename: C
authors.initials: C
authors.lastname: Narasimhan
authors.forename: C S
authors.initials: CS
authors.lastname: Lai
authors.forename: A
authors.initials: A
authors.lastname: Haas
authors.forename: J
authors.initials: J
authors.lastname: McCarthy
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004228:Dithionitrobenzoic Acid; D005353:Fibronectins / Q000097:blood*; D006801:Humans; D010446:Peptide Fragments / Q000032:analysis; D011485:Protein Binding; D013438:Sulfhydryl Compounds / Q000032:analysis*
chemical_list: D005353:Fibronectins; D010446:Peptide Fragments; D013438:Sulfhydryl Compounds; D004228:Dithionitrobenzoic Acid