The Membrane-proximal Intracellular Domain of the Epidermal Growth Factor Receptor Underlies Negative Cooperativity in Ligand Binding
The Membrane-proximal Intracellular Domain of the Epidermal Growth Factor Receptor Underlies Negative Cooperativity in Ligand Binding
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DOI：
10.1074/jbc.m111.274175
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发表时间：
2011-12-30
影响因子：
4.8
通讯作者：
Pike, Linda J.
中科院分区：
文献类型：
--
作者：
Adak, Sangeeta;Yang, Katherine S.;Pike, Linda J.
EGF的结合诱导其受体的二聚化，导致其细胞内酪氨酸激酶活性的刺激。激酶激活发生在不对称二聚体的情况下，其中一个激酶结构域充当另一个激酶结构域的激活剂，但本身不被激活。配体结合如何与这种不对称二聚体的形成和动力学相关尚不清楚。EGF与其受体的结合是负协同的，也就是说，EGF与二聚体上的第二个位点的亲和力低于与二聚体上的第一个位点的亲和力。在这项研究中，我们分析了结合I-125-EGF的一系列EGF受体突变体在细胞内的质膜结构域，并证明，该区域的最膜近端部分起着重要的作用，负协同性的EGF受体的成因。这些数据与EGF与二聚体上的第一个位点结合诱导形成一个不对称激酶二聚体的模型一致。EGF与第二位点的结合需要破坏初始的不对称二聚体，并允许形成相互的不对称二聚体。因此，与第二位点结合的一些能量用于重新定向第一不对称二聚体，导致较低的结合亲和力和观察到的负协同性。
The binding of EGF induces dimerization of its receptor, leading to the stimulation of its intracellular tyrosine kinase activity. Kinase activation occurs within the context of an asymmetric dimer in which one kinase domain serves as the activator for the other kinase domain but is not itself activated. How ligand binding is related to the formation and dynamics of this asymmetric dimer is not known. The binding of EGF to its receptor is negatively cooperative-that is, EGF binds with lower affinity to the second site on the dimer than to the first site on the dimer. In this study, we analyzed the binding of I-125-EGF to a series of EGF receptor mutants in the intracellular juxtamembrane domain and demonstrate that the most membrane-proximal portion of this region plays a significant role in the genesis of negative cooperativity in the EGF receptor. The data are consistent with a model in which the binding of EGF to the first site on the dimer induces the formation of one asymmetric kinase dimer. The binding of EGF to the second site is required to disrupt the initial asymmetric dimer and allow the formation of the reciprocal asymmetric dimer. Thus, some of the energy of binding to the second site is used to reorient the first asymmetric dimer, leading to a lower binding affinity and the observed negative cooperativity.