Severne Y, Kanarek L, Vauquelin G
Naunyn Schmiedebergs Arch Pharmacol. 1986 Mar;332(3):247-52. doi: 10.1007/BF00504862.
Agonist and antagonist binding characteristics of beta-adrenoceptors in turkey erythrocyte ghosts were determined at different temperatures ranging between 7 degrees C and 42 degrees C. [3H]-DHA saturation binding experiments revealed that the antagonist-receptor interaction is entropy-driven with a small enthalpic contribution. Isoproterenol/[3H]-DHA competition binding followed the law of mass action at all the investigated temperatures. The agonist-receptor interaction is enthalpy driven with a small unfavorable decrease in entropy. This is consistent with the agonist's ability to favor an endoenergetic transconformation of the receptors. Only part of the agonist-bound receptors can undergo functional coupling to the stimulatory component of the adenylate cyclase system (Ns). This coupling process is associated with "locking-in" of the agonist and becomes persistent in the presence of the alkylating reagent N-ethylmaleimide. The number of agonist/N-ethylmaleimide-sensitive sites (i.e. coupling-prone receptors) increases with the temperature until it reaches a plateau value of 50% between 27-32 degrees C. Qualitatively similar data were obtained for rat lung and turkey erythrocyte membranes. These observations suggest that the whole receptor population can undergo agonist-mediated conformational changes but that only part of them can couple to Ns.
在7摄氏度至42摄氏度的不同温度下，测定了火鸡红细胞膜中β - 肾上腺素能受体的激动剂和拮抗剂结合特性。[3H]-DHA饱和结合实验表明，拮抗剂与受体的相互作用是由熵驱动的，焓的贡献较小。在所有研究温度下，异丙肾上腺素/[3H]-DHA竞争结合均遵循质量作用定律。激动剂与受体的相互作用是由焓驱动的，同时熵有少量不利的降低。这与激动剂促进受体的内吸能构象转变的能力一致。只有部分与激动剂结合的受体能够与腺苷酸环化酶系统（Ns）的刺激成分发生功能性偶联。这种偶联过程与激动剂的“锁定”有关，并且在烷基化试剂N - 乙基马来酰亚胺存在时会持续存在。激动剂/N - 乙基马来酰亚胺敏感位点（即易于偶联的受体）的数量随温度升高而增加，直到在27 - 32摄氏度之间达到50%的平台值。在大鼠肺和火鸡红细胞膜上获得了定性相似的数据。这些观察结果表明，整个受体群体都可以经历激动剂介导的构象变化，但只有部分受体能够与Ns偶联。
