Insulin binds the insulin receptor

Under normal physiological conditions blood glucose levels are kept under tight control by a series of regulated steps that ensure glucose homeostasis. Upon feeding glucose levels rise and in response to this the body secretes insulin from pancreatic beta-cells into the blood. At physiological concentrations insulin is present in the blood in its monomeric form. The insulin receptor is a tetramer, consisting of two alpha and two beta chains, which are produced by cleavage of a single translated peptide chain (Schenker & Kohanski 1991). Binding of insulin to its receptor occurs on the receptor alpha-subunits. There are two binding domains involved on the receptor (L1 and L2) and it is thought that the amino-terminus of insulin binds with L1 on one of the alpha-subunits and the carboxyterminus with L2 on the other alpha-subunit.<p>The binding of insulin to its receptor causes a conformational change in the alpha-subunits. This in turn produces a conformational change in the beta-subunits leading to the activation of the intrinsic insulin receptor tyrosine kinase.

在生理条件下，血糖水平通过一系列调节步骤得到严格控制，以确保葡萄糖稳态。进食后，血糖水平上升，作为对此反应，身体从胰腺的β细胞中分泌胰岛素进入血液。在生理浓度下，胰岛素以单体形式存在于血液中。胰岛素受体由两个α链和两个β链组成，这些链由单个翻译肽链的切割产生（Schenker & Kohanski 1991）。胰岛素与其受体的结合发生在受体α亚基上。受体内涉及两个结合域（L1和L2），据信胰岛素的氨基端与一个α亚基上的L1结合，而羧基端则与另一个α亚基上的L2结合。胰岛素与其受体的结合导致α亚基构象变化，进而引发β亚基构象变化，最终激活内源胰岛素受体酪氨酸激酶。