Solution structure of human plasma fibronectin as a function of NaCl concentration determined by small-angle X-ray scattering.
The structure of human plasma fibronectin in 50 mM Tris-HCl buffer, pH 7.4, containing varying concentrations of NaCl, has been investigated using the small-angle X-ray method. Below 0.3 M NaCl the overall structure of the molecule is disc-shaped; at 0 M NaCl the axial ratio of the disc is about 1:7 and between 0.1 M to 0.3 M it is slightly more asymmetric, with an axial ratio of 1:10. At about 0.3 M NaCl there is a reversible transition to a more open structure, and, from 0.3 M up to 1.1 M NaCl the small-angle X-ray data can be explained by models consisting of ensembles of flexible, non-overlapping, bead-chains generated by a Monte Carlo procedure. Within this concentration range there is a gradual increase in the stiffness of the chains, as well as a decrease in bead radius, which indicates that the molecule becomes more open when the NaCl concentration is increased. The transition to a more open structure is also demonstrated by the average radius of gyration which increases gradually from 8.26 nm at 0 M NaCl to 8.75 nm at physiological or near-physiological conditions, and up to 16.2 nm at 1.1 M NaCl.
Sjöberg
B
B
Department of Medical Biochemistry, University of Göteborg, Sweden.
Eriksson
M
M
Osterlund
E
E
Pap
S
S
Osterlund
K
K
D005353:Fibronectins / Q000097:blood* / Q000648:ultrastructure; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D009010:Monte Carlo Method; D009994:Osmolar Concentration; D011487:Protein Conformation; D012965:Sodium Chloride / Q000494:pharmacology; D012996:Solutions; D014961:X-Ray Diffraction / Q000379:methods
D005353:Fibronectins; D046911:Macromolecular Substances; D012996:Solutions; D012965:Sodium Chloride