Tyrosine modification enhances metal-ion binding.
Tyrosine modification enhances metal-ion binding.
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酪氨酸的修饰增强了金属离子结合。
DOI：
10.1042/bj20081059
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发表时间：
2008-11-15
影响因子：
4.1
通讯作者：
Norton, Raymond S.
中科院分区：
文献类型：
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作者：
Baldwin, Graham S.;Bailey, Michael F.;Shehan, B. Philip;Sims, Loulia;Norton, Raymond S.
酪氨酸硫酸化是许多蛋白质的常见修饰，并且磷酸化酪氨酸残基的能力是许多生长因子受体的固有性质。我们已经利用肽激素胆囊收缩素（CCK 8），这自然发生在硫酸化和非硫酸化的形式，作为一个模型来研究酪氨酸修饰对金属离子结合的影响。对Fe 3+离子结合的吸光度和荧光发射的变化表明，酪氨酸硫酸化或磷酸化将化学计量从1增加到2，而不会显著影响亲和力（0.6-2.8 μM，pH 6.5）。用钙离子选择性电极测定钙离子结合，发现磷酸化CCK 8结合两个Ca 2+离子。CCK 8和硫酸化CCK 8各自仅结合一种具有较低亲和力的Ca 2+离子。Ca 2+、Zn 2+或Bi 3+离子与磷酸化CCK 8的结合没有引起吸光度的任何变化，但在随后加入Fe 3+离子时显著增加吸光度的变化。我们的研究结果表明，酪氨酸修饰可以增加金属离子与肽结合的亲和力，并暗示金属离子可以直接调节许多信号通路。
Tyrosine sulphation is a common modification of many proteins, and the ability to phosphorylate tyrosine residues is an intrinsic property of many growth factor receptors. We have utilized the peptide hormone cholecystokinin (CCK8), which occurs naturally in both sulphated and unsulphated forms, as a model to investigate the effect of tyrosine modification on metal ion binding. The changes in absorbance and fluorescence emission on Fe3+ ion binding indicated that tyrosine sulphation or phosphorylation increased the stoichiometry from 1 to 2, without greatly affecting the affinity (0.6–2.8 μM at pH 6.5). Measurement of calcium binding with a calcium-selective electrode revealed that phosphorylated CCK8 bound two Ca2+ ions. CCK8 and sulphated CCK8 each bound only one Ca2+ ion with lower affinity. Binding of Ca2+, Zn2+ or Bi3+ ions to phosphorylated CCK8 did not cause any change in absorbance, but substantially increased the change in absorbance on subsequent addition of Fe3+ ions. Our results demonstrate that tyrosine modification may increase the affinity of metal ion binding to peptides, and imply that metal ions may directly regulate many signaling pathways.