Potentiation of epidermal growth factor receptor protein-tyrosine kinase activity by sulfate.
Potentiation of epidermal growth factor receptor protein-tyrosine kinase activity by sulfate.
复制标题
硫酸盐增强表皮生长因子受体蛋白酪氨酸激酶活性。
DOI：
10.1016/0167-4889(92)90052-d
复制
发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Bertics,PJ
中科院分区：
文献类型：
--
作者：
Hubler,L;Kher,U;Bertics,PJ
表皮生长因子（EGF）受体的蛋白酪氨酸激酶活性对表皮生长因子刺激的细胞生长至关重要，尽管对其酶活性的分子细节知之甚少。以往的研究发现，硫酸铵（(NH4)2SO4）等因子可以刺激EGF受体激酶活性，但（NH4）2SO4诱导这种作用的方式尚不清楚。因此，我们探索了（NH4） 2so4增强酪氨酸激酶活性的过程，以便更好地了解（NH4） 2so4激活的分子事件，以及EGF受体的动力学性质和机制。在这项研究中，添加最佳浓度的（NH4）2SO4（250 mM）导致对肽底物血管紧张素II的激酶活性的5倍刺激。硫酸盐基团主要参与了这一作用，因为其他含有SO42−的盐也类似地增加了激酶活性，而含有Cl−和F−的盐的作用较小，二价盐如HPO42−在1 mM或更多剂量时具有抑制作用。此外，（NH4） 2so4对EGF受体激酶的激活与溶液的离子强度或电导率的变化没有严格的相关性。然而，一些证据表明，SO42−直接改变了EGF受体激酶的动力学性质：(1)在（NH4）2SO4存在下，EGF受体磷酸化血管紧张素II的最大速度（Vmax）和km （ATP）显着提高。(2)在没有（NH4）2SO4的情况下，EGF受体激酶活性需要Mn2+或Mg2+，而在有（NH4）2SO4的情况下，只有Mn2+支持激酶活性的增加。(3)硫酸铵的加入改变了ADP对血管紧张素II的产物抑制模式，表明在（NH4） 2so4存在的情况下，酶-血管紧张素II-ADP复合物可以形成，而在没有（NH4） 2so4的情况下则不能形成。(4)近最大自磷酸化速率不受（NH4）2SO4的影响，但表观km （ATP）显著增加。根据这些结果，我们提出了一个（NH4） 2so4刺激EGF受体激酶活性的模型，其中SO42 -直接与受体或受体- mn2 +-ATP复合物相互作用，并改变反应物结合和酪氨酸激酶的催化效率。
The protein-tyrosine kinase activity of the epidermal growth factor (EGF) receptor is critical for EGF-stimulated cell growth, although little is known about the molecular details of its enzymatic activity. Previous studies have found that EGF receptor kinase activity can be stimulated by factors such as ammonium sulfate ((NH4)2SO4), but the manner in which (NH4)2SO4induces this effect is unclear. Therefore, we have explored the processes by which (NH4)2SO4potentiated tyrosine kinase activity to better understand not only the molecular events involved in (NH4)2SO4activation, but also the kinetic properties and mechanism of the EGF receptor. In this study, the addition of an optimum concentration of (NH4)2SO4(250 mM) resulted in a 5-fold stimulation of kinase activity toward the peptide substrate, angiotensin II. The sulfate group is primarily involved in this action, since other salts containing SO42−increased kinase activity similarly, whereas salts containing Cl−and F−had less of an effect, and divalent salts such as HPO42−were inhibitory at doses of 1 mM or more. In addition, EGF receptor kinase activation by (NH4)2SO4did not strictly correlate with changes in the ionic strength or conductivity of the solution. However, several lines of evidence suggest that SO42−directly alters the kinetic properties of the EGF receptor kinase: (1) the maximum velocity (Vmax) andKm(ATP) for EGF receptor phosphorylation of angiotensin II were substantially higher in the presence of (NH4)2SO4. (2) EGF receptor kinase activity in the absence of (NH4)2SO4required either Mn2+or Mg2+, yet in the presence of (NH4)2SO4, only Mn2+supported the increase in kinase activity. (3) Ammonium sulfate addition altered the product inhibition pattern of ADP versus angiotensin II, suggesting that an enzyme-angiotensin II-ADP complex can form in the presence of (NH4)2SO4but not in its absence. (4) The near-maximal rate of self-phosphorylation was not affected by (NH4)2SO4, but the apparentKm(ATP) was greatly increased. From these results, we propose a model for (NH4)2SO4stimulation of EGF receptor kinase activity in which SO42−interacts directly with the receptor or receptor-Mn2+-ATP complex and alters reactant binding and the catalytic efficiency of the tyrosine kinase.