High structural flexibility has been reported in the central region of BRCA1, which hinders the structural and functional evaluations of mutations identified in the domain. Additionally, the need to categorize variants of unknown significance (VUS) has increased due to the growth in the number of variants reported in clinical settings. Therefore, unraveling the disease-causing mechanism of VUS identified in different functional domains of BRCA1 is still challenging. The current study uses a multidisciplinary approach to assess the structural impact of BRCA1 Arg866Cys mutation discovered in the central domain of BRCA1. The structural alterations have been characterized using Circular-Dichroism spectroscopy, nano-DSF, and molecular-dynamics simulations. BRCA1 Arg866Cys mutant demonstrated more flexibility and lesser affinity to DNA than the wild-type protein. The BRCA1(759–1064) wild-type protein was shown to be a βII-rich protein with an induced D-O transition in the presence of DNA and 2,2,2-Trifluoroethanol (TFE). The protein's alpha-helical composition did not significantly change in the presence of TFE, besides an increase in β-turns and loops. Under Transmission Electron Microscopes (TEM), amyloid-like fibrils structure was detected for Arg866Cys mutant whereas the wild-type protein showed amorphous aggregates. An increased ThT fluorescence indicated β-rich composition and aggregation-prone behaviour for BRCA1 wild-type protein, while the fluorescence intensity was significantly quenched in the Arg866Cys mutant. Furthermore, increased conformational flexibility in the Arg866Cys variant was observed by principal component analysis. This work aims to comprehend the inherently disordered region of BRCA1 as well as the impact of missense mutations on folding patterns and binding to DNA for functional aspects.

据报道，BRCA1 的中心区域具有高度的结构灵活性，这阻碍了对该结构域中发现的突变的结构和功能评估。此外，由于临床环境中报告的变异数量的增长，对意义不明的变异 (VUS) 进行分类的需求也有所增加。因此，阐明 BRCA1 不同功能域中发现的 VUS 的致病机制仍然具有挑战性。目前的研究采用多学科方法来评估 BRCA1 中央域发现的 BRCA1 Arg866Cys 突变的结构影响。使用圆二色光谱、纳米 DSF 和分子动力学模拟对结构变化进行了表征。与野生型蛋白相比，BRCA1 Arg866Cys 突变体表现出更大的灵活性和更低的 DNA 亲和力。BRCA1(759–1064) 野生型蛋白被证明是一种富含 βII 的蛋白，在 DNA 和 2,2,2-三氟乙醇 (TFE) 存在的情况下可诱导 DO 转变。TFE 存在时，除了 β 转角和环增加外，蛋白质的 α 螺旋组成没有显着变化。在透射电子显微镜 (TEM) 下，Arg866Cys 突变体检测到类淀粉样原纤维结构，而野生型蛋白则显示出无定形聚集体。ThT荧光增加表明 BRCA1 野生型蛋白具有富含 β 的成分和易于聚集的行为，而 Arg866Cys 突变体的荧光强度显着猝灭。此外，通过主成分分析观察到 Arg866Cys 变体的构象灵活性增加。这项工作旨在了解 BRCA1 固有的无序区域，以及错义突变对折叠模式和与 DNA 结合的功能方面的影响。