Vallée-Bélisle Alexis, Ricci Francesco, Plaxco Kevin W
Department of Chemistry and Biochemistry, Interdepartmental Program in Biomolecular Science and Engineering, University of California, Santa Barbara, CA 93106, USA.
Proc Natl Acad Sci U S A. 2009 Aug 18;106(33):13802-7. doi: 10.1073/pnas.0904005106. Epub 2009 Aug 5.
Binding-induced biomolecular switches are used throughout nature and, increasingly, throughout biotechnology for the detection of chemical moieties and the subsequent transduction of this detection into useful outputs. Here we show that the thermodynamics of these switches are quantitatively described by a simple 3-state population-shift model, in which the equilibrium between a nonbinding, nonsignaling state and the binding-competent, signaling state is shifted toward the latter upon target binding. Because of this, their performance is determined by the tradeoff inherent to their switching thermodynamics; while a switching equilibrium constant favoring the nonbinding, nonsignaling, conformation ensures a larger signal change (more molecules are poised to respond), it also reduces affinity (binding must overcome a more unfavorable conformational free energy). We then derive and employ the relationship between switching thermodynamics and switch signaling to rationally tune the dynamic range and detection limit of a representative structure-switching biosensor, a molecular beacon, over 4 orders of magnitude. These findings demonstrate that the performance of biomolecular switches can be rationally tuned via mutations that alter their switching thermodynamics and suggest a mechanism by which the performance of naturally occurring switches may have evolved.
结合诱导的生物分子开关在自然界中广泛应用，并且在生物技术领域的应用也日益增多，用于检测化学基团，并将这种检测结果转化为有用的输出。在此，我们表明这些开关的热力学可以通过一个简单的三态群体转移模型进行定量描述，在该模型中，非结合、无信号状态与具有结合能力的信号状态之间的平衡在目标结合时会向后者转移。因此，它们的性能取决于其开关热力学所固有的权衡；虽然有利于非结合、无信号构象的开关平衡常数可确保更大的信号变化（更多分子准备做出响应），但这也会降低亲和力（结合必须克服更不利的构象自由能）。然后，我们推导并运用开关热力学与开关信号之间的关系，合理调节一种代表性的结构转换生物传感器——分子信标的动态范围和检测限，范围超过4个数量级。这些发现表明，生物分子开关的性能可以通过改变其开关热力学的突变进行合理调节，并提出了一种自然发生的开关性能可能进化的机制。
