Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4M1, Canada.
Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON L8S 4M1, Canada.
Sci Adv. 2020 Jun 19;6(25):eabb1250. doi: 10.1126/sciadv.abb1250. eCollection 2020 Jun.
The functional response of a signaling system to an allosteric stimulus often depends on subcellular conditions, a phenomenon known as pluripotent allostery. For example, a single allosteric modulator, Rp-cAMPS, of the prototypical protein kinase A (PKA) switches from antagonist to agonist depending on MgATP levels. However, the mechanism underlying such pluripotent allostery has remained elusive for decades. Using nuclear magnetic resonance spectroscopy, ensemble models, kinase assays, and molecular dynamics simulations, we show that allosteric pluripotency arises from surprisingly divergent responses of highly homologous tandem domains. The differential responses perturb domain-domain interactions and remodel the free-energy landscape of inhibitory excited states sampled by the regulatory subunit of PKA. The resulting activation threshold values are comparable to the effective free energy of regulatory and catalytic subunit binding, which depends on metabolites, substrates, and mutations, explaining pluripotent allostery and warranting a general redefinition of allosteric targets to include specific subcellular environments.
信号系统对别构刺激的功能反应通常取决于亚细胞条件，这种现象被称为多效性别构。例如，典型蛋白激酶 A（PKA）的单个别构调节剂 Rp-cAMPS 根据 MgATP 水平从拮抗剂转变为激动剂。然而，这种多效性别构的机制几十年来一直难以捉摸。使用核磁共振波谱、整体模型、激酶测定和分子动力学模拟，我们表明别构多效性源于高度同源串联结构域的惊人差异反应。这种差异反应会破坏结构域-结构域相互作用，并重塑 PKA 调节亚基采样的抑制激发态的自由能景观。由此产生的激活阈值值与调节和催化亚基结合的有效自由能相当，这取决于代谢物、底物和突变，解释了多效性别构，并需要重新定义别构靶点以包括特定的亚细胞环境。
