Epistasis is a major determinant in the emergence of novel protein function. In allosteric proteins, direct interactions between inducer-binding mutations propagate through the allosteric network, manifesting as epistasis at the level of biological function. Elucidating this relationship between local interactions and their global effects is essential to understanding evolution of allosteric proteins. We integrate computational design, structural and biophysical analysis to characterize the emergence of novel inducer specificity in an allosteric transcription factor. Adaptive landscapes of different inducers of the engineered mutant show that a few strong epistatic interactions constrain the number of viable sequence pathways, revealing ridges in the fitness landscape leading to new specificity. Crystallographic evidence shows a single mutation drives specificity by reshaping the binding pocket. Comparison of biophysical and functional landscapes emphasizes the nonlinear relationship between local inducer affinity and global function (allostery). Our results highlight the functional and evolutionary complexity of allosteric proteins.

中文翻译：

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上位性塑造了变构特异性转换的适应性景观

上位性是新蛋白质功能出现的主要决定因素。在变构蛋白中，诱导剂结合突变之间的直接相互作用通过变构网络传播，表现为生物学功能水平的上位性。阐明局部相互作用与其整体效应之间的关系对于理解变构蛋白的进化至关重要。我们集成了计算设计，结构和生物物理分析，以表征变构转录因子中新型诱导物特异性的出现。工程突变体的不同诱导物的适应性景观表明，一些强烈的上位性相互作用限制了可行序列途径的数量，揭示了适应性景观中的山脊导致了新的特异性。晶体学证据表明，单个突变通过重塑结合口袋来驱动特异性。生物物理景观和功能景观的比较强调了局部诱导物亲和力与全局功能（别构）之间的非线性关系。我们的结果突出了变构蛋白的功能和进化复杂性。