Guanine nucleotide regulation of the interconversion of the two-state hepatic glucagon receptor system of rat.
Guanine nucleotide regulation of the interconversion of the two-state hepatic glucagon receptor system of rat.
复制标题
鸟嘌呤核苷酸对大鼠两态肝胰高血糖素受体系统相互转化的调节。
DOI：
10.1016/0003-9861(88)90405-5
复制
发表时间：
1988
影响因子：
3.9
通讯作者：
Gurd,RS
中科院分区：
文献类型：
--
作者：
Wyborski,RJ;Horwitz,EM;Jenkins,WT;Mormol,JS;Gurd,RS
为了研究鸟嘌呤核苷酸是否调节两种状态的肝胰高血糖素受体的相互转化，我们利用胰高血糖素结合到部分纯化的大鼠肝质膜的动力学测定。胰高血糖素在30 °C下的解离在不存在或存在GTP的情况下表现出双指数特征，表明先前在完整肝细胞中观察到的系统不依赖于细胞内调节剂。在每种情况下，受体都经历了从低亲和力到高亲和力状态的时间依赖性转化。然而，GTP降低了处于高亲和力状态的受体的分数。稳定低亲和力状态的等级顺序为Gpp（NH）p > GTP > GDP> GMP =无核苷酸。通过增加GTP浓度的竞争结合试验数据，可以计算出平衡常数，在不存在GTP的情况下，胰高血糖素和受体的平衡常数为3.32 nm，在存在GTP的情况下，胰高血糖素和受体的平衡常数为18.6 nm，受体和推测与N蛋白连接的GTP的结合常数为1.55 μ m，胰高血糖素受体复合物与GTP的结合为8.86 μ m，推测GTP与N蛋白连接。胰高血糖素与受体的结合在不存在和存在GTP的情况下都是非合作的，将该系统与β-肾上腺素能系统区分开来。对于GTP，由于报道的相对亲和力，结合到低亲和力状态是有利的。因此，GTP通过减缓受体从低亲和力到高亲和力形式的转化来调节活化。
To investigate whether guanine nucleotides regulate interconversion of the two-state hepatic glucagon receptor we have utilized kinetic assays of glucagon binding to partially purified rat liver plasma membranes. Dissociation of glucagon at 30 °C exhibited biexponential character in either the absence or presence of GTP, indicating that the system previously seen in intact hepatocytes is independent of intracellular modulators. In each case the receptors underwent a time-dependent conversion from a low affinity to a high affinity state. However, GTP decreased the fraction of receptors in the high affinity state. The rank order for stabilizing the low affinity state was Gpp(NH)p > GTP > GDP ≫ GMP = no nucleotides. Data from competition binding assays with increasing concentrations of GTP allow calculation of equilibrium constants which are 3.32 nmfor glucagon and receptor in the absence of GTP, 18.6 nmfor glucagon and receptor in the presence of GTP, 1.55 μmfor the association of receptor and GTP presumably linked to an N protein, and 8.86 μmfor the association of the glucagon-receptor complex and GTP again presumably linked to an N protein. Glucagon binding to receptor is noncooperative in both the absence and presence of GTP, distinguishing this system from the β-adrenergic system. With GTP, binding to the low affinity state is favored because of the relative affinities reported. Therefore, GTP regulates the activation by slowing the conversion of the receptor from a low affinity to high affinity form.