Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
Nat Commun. 2021 Sep 21;12(1):5562. doi: 10.1038/s41467-021-25826-7.
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 designed 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. The structure of the designed mutant shows that a striking change in inducer orientation still retains allosteric function. Comparing biophysical and functional properties suggests a nonlinear relationship between inducer binding affinity and allostery. Our results highlight the functional and evolutionary complexity of allosteric proteins.
上位性是新蛋白质功能出现的主要决定因素。在别构蛋白中，诱导剂结合突变之间的直接相互作用通过别构网络传播，在生物功能水平上表现为上位性。阐明这种局部相互作用与其全局效应之间的关系，对于理解别构蛋白的进化至关重要。我们将计算设计、结构和生物物理分析相结合，以描述别构转录因子中新型诱导特异性的出现。不同诱导剂的设计突变体的适应景观表明，少数强上位性相互作用限制了可行序列途径的数量，揭示了导致新特异性的适应性景观中的脊。设计突变体的结构表明，诱导剂取向的显著变化仍然保留着别构功能。比较生物物理和功能特性表明，诱导剂结合亲和力和变构之间存在非线性关系。我们的研究结果突出了别构蛋白的功能和进化复杂性。
