Mechanism of agonist and antagonist binding to alpha 2 adrenergic receptors: evidence for a precoupled receptor-guanine nucleotide protein complex.
Mechanism of agonist and antagonist binding to alpha 2 adrenergic receptors: evidence for a precoupled receptor-guanine nucleotide protein complex.
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激动剂和拮抗剂与α2肾上腺素能受体结合的机制：预偶联受体-鸟嘌呤核苷酸蛋白复合物的证据。
作者：
R. Neubig;R. Gantzos;William J. Thomsen
The alpha 2 adrenergic receptor (AR) inhibits adenylate cyclase via an interaction with Ni, a guanine nucleotide binding protein. The early steps involved in the activation of the alpha 2 AR by agonists and the subsequent interaction with Ni are poorly understood. In order to better characterize these processes, we have studied the kinetics of ligand binding to the alpha 2 AR in human platelet membranes on the second time scale. Binding of the alpha 2 antagonist [3H]yohimbine was formally consistent with a simple bimolecular reaction mechanism with an association rate constant of 2.5 X 10(5) M-1 s-1 and a dissociation rate constant of 1.11 X 10(-3) s-1. The low association rate constant suggests that this is not a diffusion-limited reaction. Equilibrium binding of the alpha 2 adrenergic full agonist [3H]UK 14,304 was characterized by two binding affinities: Kd1 = 0.3-0.6 nM and Kd2 = 10 nM. The high-affinity binding corresponds to approximately 65% and the low-affinity binding to 35% of the total binding. The kinetics of binding of [3H]UK 14,304 were complex and not consistent with a mass action interaction at one or more independent binding sites. The dependence of the kinetics on [3H]UK 14,304 concentration revealed a fast phase with an apparent bimolecular reaction constant kappa + of 5 X 10(6) M-1 s-1. The rate constants and amplitudes of the slow phase of agonist binding were relatively independent of ligand concentration. These results were analyzed quantitatively according to several variants of the "ternary complex" binding mechanism. In the model which best accounted for the data, (1) approximately one-third of the alpha 2 adrenergic receptor binds agonist with low affinity and is unable to couple with a guanine nucleotide binding protein (N protein), (2) approximately one-third is coupled to the N protein prior to agonist binding, and (3) the remainder interacts by a diffusional coupling of the alpha 2 AR with the N protein or a slow, ligand-independent conformational change of the alpha 2 AR-N protein complex. The rates of interaction of liganded and unliganded receptor with N protein are estimated.
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平行观察完整血小板中α2-肾上腺素能受体的占据情况及其抑制腺苷酸环化酶的能力。
影响因子：
3.6
作者：
Macfarlane,DE;Stump,DC
通讯作者：
Stump,DC
使用三种纯化的蛋白质重建儿茶酚胺刺激的腺苷酸环化酶活性。
DOI：
--
发表时间：
1985
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
May,DC;Ross,EM;Gilman,AG;Smigel,MD
通讯作者：
Smigel,MD
激动剂和拮抗剂标记的血小板 α2 肾上腺素受体的不同沉降特性。
DOI：
10.1016/0006-291x(81)91941-0
发表时间：
1981
影响因子：
3.1
作者：
Michel,T;Hoffman,BB;Lefkowitz,RJ;Caron,MG
通讯作者：
Caron,MG
激动剂与完整细胞上的 β-肾上腺素能受体高亲和力结合。
DOI：
10.1073/pnas.80.12.3553
发表时间：
1983
影响因子：
11.1
作者：
Toews,ML;Harden,TK;Perkins,JP
通讯作者：
Perkins,JP
药物-受体相互作用的定量分析：I.动力学和平衡特性的测定。
影响因子：
6.1
作者：
Weiland,GA;Molinoff,PB
通讯作者：
Molinoff,PB