Almagor H, Levitzki A
Fritz Haber Research Center for Molecular Dynamics, Hebrew University of Jerusalem, Israel.
Proc Natl Acad Sci U S A. 1990 Sep;87(17):6482-6. doi: 10.1073/pnas.87.17.6482.
The determination of receptor-ligand dissociation constants from displacement data has been restricted until recently to the condition of receptor saturation, in which the concentration of receptor is negligible as compared to the displaced ligand and the displacing ligand used. This restriction has lately been removed since an accurate method has been developed for the determination of the dissociation constants for all experimental conditions for a system that includes a single type of binding site. In many cases, however, there are two types of receptor binding sites that exhibit different affinities toward the ligand. The present study provides an analytic solution for the problem of determination of the two dissociation constants as well as the proportion of the two receptor types. The formal derivation of the equations is described, along with analysis of a displacement simulation. The sensitivity of the method to the ratio between the two dissociation constants is also investigated. The application of the method is demonstrated for the analysis of the binding of beta-adrenergic receptors to the agonist isoproterenol as monitored by the displacement of the beta-antagonist 125I-labeled cyanopindolol.
直到最近，根据置换数据确定受体 - 配体解离常数还局限于受体饱和的条件，即在该条件下，与被置换配体和所用置换配体相比，受体浓度可忽略不计。由于已开发出一种精确方法来测定包含单一类型结合位点的系统在所有实验条件下的解离常数，这种限制最近已被消除。然而，在许多情况下，存在两种对配体表现出不同亲和力的受体结合位点。本研究为确定两个解离常数以及两种受体类型的比例这一问题提供了一种解析解决方案。文中描述了方程的形式推导以及置换模拟分析。还研究了该方法对两个解离常数之间比率的敏感性。通过β拮抗剂125I标记的氰吲哚洛尔的置换监测，证明了该方法在分析β肾上腺素能受体与激动剂异丙肾上腺素结合中的应用。
