Fast kinetic studies on the allosteric interactions between acetylcholine receptor and local anesthetic binding sites.
Fast kinetic studies on the allosteric interactions between acetylcholine receptor and local anesthetic binding sites.
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乙酰胆碱受体和局麻药结合位点之间变构相互作用的快速动力学研究。
DOI：
10.1111/j.1432-1033.1979.tb12894.x
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
J. Changeux
中科院分区：
文献类型：
--
作者：
T. Heidmann;J. Changeux
预孵育的受体丰富的膜片段从鱼雷marmorata与叔胺局部麻醉剂和几种毒素，如histrionicotoxin，crotoxin和铜蓝毒素，修改的幅度和时间过程的松弛监测后，快速混合的膜片段与荧光激动剂，Dns-C6-Cho。特别是，快速松弛过程的幅度，这是成比例的乙酰胆碱受体位点的分数在高亲和力状态，增加;相应地，速率常数的“慢”和“中间”松弛过程也增加了10倍（除了与histrionicotoxin），而在一个更高的范围内的局部麻醉药浓度的“快速”松弛过程的速率常数降低。的数据占由乙酰胆碱调节器的双态模型，假设不同的结合位点胆碱能激动剂和局部麻醉剂和变构相互作用这两类网站之间的局部麻醉剂稳定的调节剂在一个高亲和力的状态，即使在没有激动剂，和修改的速率常数之间的低亲和力和高亲和力的状态相互转换。该模型占的“缓慢”的荧光增加监测后，加入局部麻醉剂的悬浮液中的受体丰富的膜补充微量的Dns-C6-Cho。局部麻醉剂对“快速”松弛过程的表观速率常数的影响可以基于局部麻醉剂与乙酰胆碱受体位点的额外低亲和力结合来解释。最后，“中间”松弛过程的表观速率常数的增加可以简单地通过假设存在第三种状态来解释，第三种状态对应于“活性”状态，局部麻醉剂结合并阻断离子转运。
Preincubation of receptor-rich membrane fragments from Torpedo marmorata with tertiary amine local anesthetics and several toxins such as histrionicotoxin, crotoxin and cerulotoxin, modifies the amplitude and time course of the relaxation processes monitored upon rapid mixing of the membrane fragments with the fluorescent agonist, Dns-C6-Cho. In particular, the amplitude of the rapid relaxation process, which is proportional to the fraction of acetylcholine receptor sites in a high-affinity state, increases; accordingly, the rate constant of the 'slow' and 'intermediate' relaxation processes also increases up to ten times (except with histrionicotoxin) whereas in a higher range of local anesthetic concentrations the rate constant of the 'rapid' relaxation process decreases. The data are accounted for by a two-state model of the acetylcholine regulator, assuming distinct binding sites for cholinergic agonists and local anesthetics and allosteric interactions between these two classes of sites; local anesthetics stabilize the regulator in a high-affinity state for agonists even in the absence of agonist, and modify the rate constants for th interconversions between the low-affinity and high-affinity states. The model accounts for the 'slow' fluorescence increase monitored upon addition of local anesthetics to a suspension of receptor-rich membranes supplemented with trace amounts of Dns-C6-Cho. The effect of local anesthetics on the apparent rate constant of the 'rapid' relaxation process can be accounted for on the basis of an additional low-affinity binding of local anesthetics to the acetylcholine receptor site. Finally the increase of the apparent rate constant of the 'intermediate' relaxation process can be simply accounted for by assuming the existence of a third state, corresponding to the 'active' state, to which local anesthetics bind and block ionic transport.