Biophys J. 2010 Sep 22;99(6):L41-3. doi: 10.1016/j.bpj.2010.07.030.
Multisite phosphorylation is a common form of posttranslational protein regulation which has been used to increase the switchlike behavior of the protein response to increasing kinase concentrations. In this letter, we show that the switchlike response of multisite phosphoproteins is strongly enhanced by nonessential phosphorylation sites, a mechanism that is robust to parameter changes and easily implemented in nature. We obtained analytic estimates for the Hill exponent (or coefficient) of the switchlike response, and we observed that a tradeoff exists between the switch and the kinase threshold for activation. This also suggests a possible evolutionary mechanism for the relatively large numbers of phosphorylation sites found in various proteins.
多位点磷酸化是一种常见的蛋白质翻译后调控形式，它被用来增加蛋白质对激酶浓度增加的开关样反应。在这封信中，我们表明，非必需磷酸化位点强烈增强了多位点磷酸蛋白的开关样反应，这种机制对参数变化具有鲁棒性，并且在自然界中很容易实现。我们获得了开关样反应的Hill 指数（或系数）的解析估计，并且我们观察到开关和激酶激活的阈值之间存在权衡。这也为在各种蛋白质中发现的相对大量的磷酸化位点提供了一种可能的进化机制。
