Department of Structural Biology Weizmann Institute of Science, Rehovot 7610001, Israel.
J Phys Chem B. 2021 Jan 14;125(1):70-73. doi: 10.1021/acs.jpcb.0c09351. Epub 2021 Jan 5.
Hill coefficients, which provide a measure of cooperativity in ligand binding, can be determined for equilibrium (or steady-state) data by measuring fractional saturation (or initial reaction velocities) as a function of ligand concentration. Hill coefficients can also be determined for transient kinetic data from plots of the observed rate constant of the ligand-promoted conformational change as a function of ligand concentration. Here, it is shown that the ratio of the values of these two Hill coefficients can provide insight into the allosteric mechanism. Cases when the value of the kinetic Hill coefficient is equal to or greater than the value of the equilibrium coefficient indicate concerted transitions whereas ratios smaller than one indicate a sequential transition. The derivations in this work are for symmetric dimers but are expected to have general applicability for homo-oligomers.
Hill 系数可用于衡量配体结合的协同性，可通过测量分数饱和（或初始反应速度）作为配体浓度的函数来确定平衡（或稳态）数据。Hill 系数也可通过从观察到的配体促进构象变化的速率常数与配体浓度的关系图中确定瞬态动力学数据。这里，表明这两个 Hill 系数的值之比可以深入了解变构机制。当动力学 Hill 系数的值等于或大于平衡系数的值时，表明协同转变；而比值小于 1 时，则表明顺序转变。这项工作的推导适用于对称二聚体，但预计对同聚寡聚体具有普遍适用性。
