Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Anal Biochem. 2012 Feb 15;421(2):433-8. doi: 10.1016/j.ab.2011.12.016. Epub 2011 Dec 16.
Cooperative binding of a ligand to multiple subsites on a protein is a common theme among enzymes and receptors. The analysis of cooperative binding data (either positive or negative) often relies on the assumption that free ligand concentration, L, can be approximated by the total ligand concentration, L(T). When this approximation does not hold, such analyses result in inaccurate estimates of dissociation constants. Presented here are exact analytical expressions for equilibrium concentrations of all enzyme and ligand species (in terms of K(d) values and total concentrations of protein and ligand) for homotropic dimeric and trimeric protein-ligand systems. These equations circumvent the need to approximate L and are provided in Excel worksheets suitable for simulation and least-squares fitting. The equations and worksheets are expanded to treat cases where binding signals vary with distinct site occupancy.
配体与蛋白质上多个亚基的协同结合是酶和受体的一个常见主题。协同结合数据（无论是正协同还是负协同）的分析通常依赖于这样一个假设，即游离配体浓度 L 可以近似为总配体浓度 L(T)。当这种近似不成立时，这种分析会导致离解常数的估计不准确。本文提出了同型二聚体和三聚体蛋白-配体系统中所有酶和配体物种（以 K(d)值和蛋白与配体的总浓度表示）的平衡浓度的确切解析表达式。这些方程避免了需要近似 L 的问题，并以适合模拟和最小二乘拟合的 Excel 工作表形式提供。这些方程和工作表被扩展到处理结合信号随不同的位点占有率而变化的情况。
