title: Hydrodynamic properties of bovine brain S-100 proteins.
abstract: The size and shape of S-100a and S-100b proteins in solution have been examined by gel filtration and ultracentrifugation in the presence and absence of Ca2+. S-100a and S-100b proteins, in the absence of Ca2+, have an intrinsic sedimentation coefficient, so20,w of 2.20 and 2.15 S, respectively and in 1 mM Ca2+ their so20,w values were decreased to 2.05 and 1.95 S, respectively, indicating an unfolding of the protein molecules. The Stokes radii of S-100a and S-100b (-Ca2+) were 23.4 A and 24.0 A and they decreased to 22.2 A and 22.3 A in the presence of Ca2+. The Ca2+ effect on S-100b greater than S-100a was in agreement with our earlier CD observations. Among the monovalent cations tested (K+, Na+ and Li+) K+ had the maximum effect on the Stokes radii and so20,w values of S-100 proteins. Since certain functions of the nervous system are accompanied by local changes in ionic concentrations of Ca2+, Na+ and K+, it is conceivable that these respective conformational changes induced in S-100 proteins by these metals may be related to their function in the brain.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium; D002414:Cations, Monovalent; D002417:Cattle; D011487:Protein Conformation; D009418:S100 Proteins / Q000378:metabolism*; D012996:Solutions
chemical_list: D002414:Cations, Monovalent; D009418:S100 Proteins; D012996:Solutions; D002118:Calcium