Specific reaction rate of acetylcholine receptor-controlled ion translocation: a comparison of measurements with membrane vesicles and with muscle cells.
Specific reaction rate of acetylcholine receptor-controlled ion translocation: a comparison of measurements with membrane vesicles and with muscle cells.
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乙酰胆碱受体控制的离子易位的特异性反应率：膜囊泡和肌肉细胞测量值的比较。
DOI：
10.1073/pnas.78.3.1361
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发表时间：
1981
影响因子：
11.1
通讯作者：
Lenchitz,B
中科院分区：
文献类型：
--
作者：
Hess,GP;Aoshima,H;Cash,DJ;Lenchitz,B
测定了乙酰胆碱受体控制离子移位的比反应速率（J）。在1 ℃的林格氏溶液（pH 7.0）中，J = 3 × 10（7）M-1 sec-1。J是一个固有常数，它是受体的特征，不依赖于含有受体的细胞的其他性质，这些性质也决定了离子易位的速率。膜囊泡（由Electrophorus electricus的电器官制备）和具有毫秒时间分辨率的流动淬灭技术被用来测量受体控制的离子易位。使用J值和受体位点和无机离子的摩尔浓度，我们计算出每个受体每毫秒转运6 × 10（3）个离子。青蛙肌肉细胞在8摄氏度以上温度下的电噪声分析[Nether，E. & Stevens，C. F.（1977）Annu.生物物理学Bioeng. 6，345-381]给出了每通道约1 × 10（4）个离子毫秒-1的值。因此，每种技术基本上给出相同的结果。因此，现在有可能将在膜囊泡和肌细胞中以两种不同方式测量受体功能时获得的结果相关联：（i）使用膜囊泡的化学动力学测量，其涉及配体结合和离子易位过程，以及（ii）肌细胞中乙酰胆碱噪声的分析[Katz，B. & Miledi，R.（1972）J. Physiol.（伦敦）224，665-699]，其允许测量穿过细胞膜的离子通道形成的基本步骤。
The specific reaction rate (J) of the acetylcholine receptor-controlled ion translocation has been determined. In eel Ringer's solution (pH 7.0) at 1 degrees C, J = 3 X 10(7) M-1 sec-1. J is an intrinsic constant that is characteristic of the receptor and independent of other properties of a receptor-containing cell that also determine the rates of ion translocation. Membrane vesicles (prepared from the electric organ of Electrophorus electricus) and a flow-quench technique that has a millisecond time resolution were used to measure the receptor-controlled ion translocation. Using the value of J and the molar concentrations of receptor sites and inorganic ions, we calculated that 6 X 10(3) ions are translocated per msec per receptor. Analysis of electrical noise in frog muscle cells at temperatures above 8 degrees C [Nether, E. & Stevens, C. F. (1977) Annu. Rev. Biophys. Bioeng. 6, 345-381] gave a value of about 1 X 10(4) ions msec-1 per channel. Thus, each technique gives essentially the same result. It is now possible, therefore, to correlate the results obtained when receptor function is measured in two different ways in membrane vesicles and in muscle cells: (i) chemical kinetic measurements, using membrane vesicles, which relate the ligand binding and ion translocation processes and (ii) analysis of acetylcholine noise in muscle cells [Katz, B. & Miledi, R. (1972) J. Physiol. (London) 224, 665-699], which allows one to measure elementary steps in the formation of ion channels through the cell membrane.