ACTIVATION KINETICS REVEAL THE NUMBER OF GLUTAMATE AND GLYCINE BINDING-SITES ON THE N-METHYL-D-ASPARTATE RECEPTOR
ACTIVATION KINETICS REVEAL THE NUMBER OF GLUTAMATE AND GLYCINE BINDING-SITES ON THE N-METHYL-D-ASPARTATE RECEPTOR
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DOI：
10.1016/0896-6273(91)90373-8
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发表时间：
1991-10-01
期刊：
影响因子：
16.2
通讯作者：
WESTBROOK, GL
中科院分区：
文献类型：
--
作者：
CLEMENTS, JD;WESTBROOK, GL
分析海马神经元外向片N-甲基-D-天冬氨酸(NMDA)通道的激活动力学，以确定每个通道的谷氨酸和甘氨酸结合位点的数目。在快速进入高浓度谷氨酸后，激活时间过程不依赖于浓度，并受到关闭但完全连接的状态和开放状态之间的转换的限制。在较低浓度时，配基结合是限速的。由两个谷氨酸结合部位组成的动力学模型最好地拟合了S型激活时间过程。在谷氨酸持续存在的情况下，甘氨酸浓度的跳跃也与双位点模型拟合得最好。激动剂和共激剂结合更好地用独立的模型来描述，而不是序贯模型。我们认为，NMDA受体至少是一个包含四个配体结合亚基的四聚体，假设每个亚基有一个结合位点。
The activation kinetics of N-methyl-D-aspartate (NMDA) channels in outside-out patches from cultured hippocampal neurons were analyzed to determine the number of glutamate and glycine binding sites per channel. Following rapid steps into high concentrations of glutamate, the activation time course was concentration-independent and limited by transitions between the shut, but fully liganded state and the open state. At lower concentrations, ligand binding was rate-limiting. The resulting sigmoidal activation time course was best fitted by a kinetic model with two glutamate binding sites. Glycine concentration jumps in the continuous presence of glutamate were also best fitted with a two-site model. Agonist and coagonist binding were better described by an independent, rather than a sequential model. We suggest that the NMDA receptor is at least a tetramer containing four ligand binding subunits, assuming a single binding site per subunit.