Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, United States.
Nuclear Magnetic Resonance Core Laboratory, University of Kansas, Lawrence, Kansas 66045, United States.
Biochemistry. 2020 Oct 20;59(41):4039-4050. doi: 10.1021/acs.biochem.0c00479. Epub 2020 Oct 1.
The tumor suppressor Adenomatous polyposis coli (APC) is a large, multidomain protein with many identified cellular functions. The best characterized role of APC is to scaffold a protein complex that negatively regulates Wnt signaling via β-catenin destruction. This destruction is mediated by β-catenin binding to centrally located 15- and 20-amino acid repeat regions of APC. More than 80% of cancers of the colon and rectum present with an mutation. Most carcinomas with mutant express a truncated APC protein that retains the ∼200-amino acid long' 15-amino acid repeat region'. This study demonstrates that the 15-amino acid repeat region of APC is intrinsically disordered. We investigated the backbone dynamics in the presence of β-catenin and predicted residues that may contribute to transient secondary features. This study reveals that the 15-amino acid region of APC retains flexibility upon binding β-catenin and that APC does not have a single, observable "highest-affinity" binding site for β-catenin. This flexibility potentially allows β-catenin to be more readily captured by APC and then remain accessible to other elements of the destruction complex for subsequent processing.
抑癌基因腺瘤性结肠息肉病（APC）是一种具有多种细胞功能的大型多结构域蛋白。APC 的最典型作用是支架蛋白复合物，通过β-连环蛋白破坏来负调控 Wnt 信号。这种破坏是通过 APC 中央位置的 15 个和 20 个氨基酸重复区域与β-连环蛋白结合来介导的。超过 80%的结肠癌和直肠癌都存在突变。大多数带有突变的癌都表达一种截短的 APC 蛋白，保留了约 200 个氨基酸长的“15 个氨基酸重复区”。本研究表明，APC 的 15 个氨基酸重复区是固有无序的。我们研究了存在β-连环蛋白时的骨干动力学，并预测了可能有助于瞬态二级特征的残基。这项研究揭示了 APC 的 15 个氨基酸区域在与β-连环蛋白结合后保持灵活性，并且 APC 没有针对β-连环蛋白的单一可观察的“最高亲和力”结合位点。这种灵活性可能使 APC 更容易捕获β-连环蛋白，然后使其能够被破坏复合物的其他成分后续处理。
