Rat Brain S100b Protein: Purification, Characterization, and Ion Binding Properties. A Comparison with Bovine S100b Protein

Abstract

We purified to homogeneity rat brain S100b protein, which constitutes about 90% of the soluble S100 protein fraction. Purified rat S100b protein comigrates with bovine S100b protein in nondenaturant system electrophoresis but differs in its amino acid composition and in its electrophoretic mobility in urea-sodium dodecyl sulfate-polyacrylamide gel with bovine S100b protein. The properties of the Ca2+ and Zn2+ binding sites on rat S100b protein were investigated by flow dialysis and by fluorometric titration, and the conformation of rat S100b in its metal-free form as well as in the presence of Ca2+ or Zn2+ was studied. The results were compared with those obtained for the bovine S100b protein. In the absence of KCl, rat brain S100b protein is characterized by two high-affinity Ca2+ binding sites with a KD of 2 X 10(-5) M and four lower affinity sites with KD about 10(-4) M. The calcium binding properties of rat S100b protein differ from bovine S100b only by the number of low-affinity calcium binding sites whereas similar Ca2+-induced conformational changes were observed for both proteins. In the presence of 120 mM KCl rat brain S100b protein bound two Zn2+-ions/mol of protein with a KD of 10(-7) M and four other with lower affinity (KD approximately equal to 10(-6) M). The occupancy of the two high-affinity Zn2+ binding sites was responsible for most of the Zn2+-induced conformational changes in the rat S100b protein. No increase in the tyrosine fluorescence quantum yield after Zn2+ binding to rat S100b was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Levels and Distribution of the Calcium‐Modulated Proteins S100 and Calmodulin in Rat C6 Glioma Cells

“…These data suggest that the levels of S 1 OOp and calmodulin are differently regulated in C6 cells. Our data are consistent with other studies that have demonstrated that Sloop is the predominant S 100 polypeptide in rat brain (Baudier et al, 1985). However, the level of Sloop in postconfluent C6 cells is lower (0.3 pg/mg protein) than that found in rat brain (3 pg/mg protein; Zimmer and Van Eldik, 1987).…”

Vanadium (V)-Induced Neurotoxicity in the Rat Central Nervous System: A Histo-Immunohistochemical Study

“…Thus, enhanced expression of GFAP appears as a ''marker'' of all types of brain injuries. S-100 protein, a glial cell cytoplasmic protein, is also a reliable indicator of astrogliosis (Baudier et al, 1985;Isobe et al, 1983).…”

The Zn2+ and Ca2+‐binding S100B and S100A1 proteins: beyond the myths

“…Chemical sequencing of the S100A1‐α and S100B‐β subunits showed that they were members of the EF‐hand calcium‐binding superfamily of proteins that includes calmodulin, troponin C and parvalbumin (Isobe & Okuyama, , ); (Kawasaki & Kretsinger, ). Studies on the physico‐chemical and structural properties of the brain homodimers S100A1 and S100B and of the heterodimer S100A1/S100B confirmed Ca 2+ binding and revealed specific high‐affinity binding of Zn 2+ by the S100B protein (Baudier & Gerard, , ; Baudier et al ., ; Baudier, Labourdette & Gerard, ; Baudier, Glasser & Gerard, ). The S100 proteins were later recognized as ubiquitous proteins also expressed in peripheral tissues (Cocchia, Michetti & Donato, ; Stefansson et al ., ; Stefansson, Wollmann & Moore, ).…”