Ions binding to S100 proteins. I. Calcium- and zinc-binding properties of bovine brain S100 alpha alpha, S100a (alpha beta), and S100b (beta beta) protein: Zn2+ regulates Ca2+ binding on S100b protein.
Ions binding to S100 proteins. I. Calcium- and zinc-binding properties of bovine brain S100 alpha alpha, S100a (alpha beta), and S100b (beta beta) protein: Zn2+ regulates Ca2+ binding on S100b protein.
复制标题
离子与 S100 蛋白结合。
DOI：
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发表时间：
1986
影响因子：
4.8
通讯作者：
D. Gérard
中科院分区：
文献类型：
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作者：
J. Baudier;N. Glasser;D. Gérard
在pH 7.5和8.3的20 mM Tris-HCl缓冲液中，流动渗析测定了钙与牛脑S100α、S100a(αβ)和S100B(β)蛋白的结合，结果表明，S100蛋白与4个钙离子eq/摩尔的蛋白质二聚体结合。因此，特定的钙结合位点被分配给α和β亚基上的典型氨基酸序列。在镁和钾的存在下，蛋白质对钙的亲和力要低得多。钾强烈地拮抗两个钙结合部位上的钙结合，这两个钙结合部位是钙离子引起S100蛋白构象变化的主要原因(可能是第二个α位点和第二个β位点)。在无二价阳离子条件下的锌结合研究揭示了S100B蛋白二聚体的8个锌结合位点/摩尔，我们推测它们对应于4个锌结合位点/β亚基。用紫外光谱方法研究锌与S100B的结合表明，蛋白质二聚体上四个高亲和力部位和四个低亲和力部位的占据导致了S100B结构的不同构象变化。高亲和力部位的锌结合通过增加蛋白对钙的亲和力和降低钾对钙结合的拮抗作用来调节钙与S100B的结合。对S100a和S100α蛋白的锌结合研究表明，含Trp的S100蛋白与锌的结合比S100B蛋白弱。对锌结合的S100a的钙结合研究证明，虽然锌结合的S100a与钙的亲和力没有增加，但与S100B蛋白一样，钙和锌的结合部位是不同的。最后，我们提供的证据表明，以前发表的关于S100B蛋白光学性质的结果之间的差异可能是由于蛋白质中的巯基被氧化所致。
Flow dialysis measurements of calcium binding to bovine brain S100 alpha alpha, S100a (alpha beta), and S100b (beta beta) proteins in 20 mM Tris-HCl buffer at pH 7.5 and 8.3 revealed that S100 proteins bind specifically 4 Ca2+ eq/mol of protein dimer. The specific calcium-binding sites had, therefore, been assigned to typical amino acid sequences on the alpha and beta subunit. The protein affinity for calcium is much lower in the presence of magnesium and potassium. Potassium strongly antagonizes calcium binding on two calcium-binding sites responsible for most of the Ca2+-induced conformational changes on S100 proteins (probably site II alpha and site II beta). Zinc-binding studies in the absence of divalent cations revealed eight zinc-binding sites/mol of S100b protein dimer that we assumed to correspond to 4 zinc-binding sites/beta subunit. Zinc binding to S100b studied with UV spectroscopy methods showed that the occupation of the four higher affinity sites and the four lower affinity sites on the protein dimer were responsible for different conformational changes in S100b structure. Zinc binding on the higher affinity sites regulates calcium binding to S100b by increasing the protein affinity for calcium and decreasing the antagonistic effect of potassium on calcium binding. Zinc-binding studies on S100a and S100 alpha alpha protein showed that the Trp-containing S100 proteins bind zinc more weakly than S100b protein. Calcium-binding studies on zinc-bound S100a proved that calcium- and zinc-binding sites were distinct although there was no increase in zinc-bound S100a affinity for calcium, as in S100b protein. Finally we provide evidence that discrepancies between previously published results on the optical properties of S100b protein probably result from oxidation of the sulfhydryl groups in the protein.