Huang Yongqi, Gao Meng, Yang Fei, Zhang Lei, Su Zhengding
Institute of Biomedical and Pharmaceutical Sciences, Hubei University of Technology, Wuhan, China.
Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei University of Technology, Wuhan, China.
Proteins. 2017 Nov;85(11):2088-2095. doi: 10.1002/prot.25364. Epub 2017 Aug 20.
The kinase-inducible domain interacting (KIX) domain of the transcriptional coactivator CBP protein carries 2 isolated binding sites (designated as the c-Myb site and the MLL site) and is capable of binding numerous intrinsically disordered transactivation domains (TADs), including c-Myb and pKID via the c-Myb site, and MLL, E2A and c-Jun via the MLL site. In this study we compared the kinetics for binding of various disordered TADs to the KIX domain via computational biophysical analyses. We found that the binding rates are heavily affected by long-range electrostatic interactions. The basal rate constants for forming the encounter complexes are similar for different KIX binding peptides, favorable electrostatic interactions between the MLL site and the peptides result in greater association rates when peptides bind to the MLL site. FOXO3a and p53 TAD each contains 2 copies of KIX binding motif and each motif interacts with both the MLL site and the c-Myb site. Our kinetics studies suggest that binding of FOXO3a or p53 TAD to the KIX domain is via a sequential mechanism, where one KIX binding motif binds to the MLL site first and then the other KIX binding motif binds to the c-Myb site. Considering the promiscuous interactions between FOXO3a and KIX, and p53 TAD and KIX, electrostatic steering simplifies the binding mechanism. This study highlights the importance of long-range electrostatic interactions in molecular recognition process involving multi-motif intrinsically disordered proteins and promiscuous interactions.
转录共激活因子CBP蛋白的激酶诱导结构域相互作用（KIX）结构域带有2个独立的结合位点（分别命名为c-Myb位点和MLL位点），能够结合众多内在无序的反式激活结构域（TAD），包括通过c-Myb位点结合c-Myb和pKID，以及通过MLL位点结合MLL、E2A和c-Jun。在本研究中，我们通过计算生物物理分析比较了各种无序TAD与KIX结构域结合的动力学。我们发现结合速率受到长程静电相互作用的严重影响。不同KIX结合肽形成相遇复合物的基础速率常数相似，当肽与MLL位点结合时，MLL位点与肽之间有利的静电相互作用导致更高的缔合速率。FOXO3a和p53 TAD各自包含2个KIX结合基序拷贝，且每个基序都与MLL位点和c-Myb位点相互作用。我们的动力学研究表明，FOXO3a或p53 TAD与KIX结构域的结合是通过一种顺序机制，其中一个KIX结合基序首先与MLL位点结合，然后另一个KIX结合基序与c-Myb位点结合。考虑到FOXO3a与KIX以及p53 TAD与KIX之间的混杂相互作用，静电引导简化了结合机制。本研究突出了长程静电相互作用在涉及多基序内在无序蛋白和混杂相互作用的分子识别过程中的重要性。
