Duchenne muscular dystrophy (DMD) gene encodes dystrophin, a large multi-domain protein. Its non-functionality leads to dystrophinopathies like DMD and Becker muscular dystrophy (BMD), for which no cure is yet available. A few therapies targeted towards specific mutations can extend the lifespan of patients, although with limited efficacy and high costs, emphasizing the need for more general treatments. Dystrophin's complex structure with poorly understood domains and the presence of multiple isoforms with varied expression patterns in different tissues pose challenges in therapeutic development. The C-terminal (CT) domain of dystrophin is less understood in terms of its structure-function, although it has been shown to perform important functional roles by interacting with another cytosolic protein, dystrobrevin. Dystrophin and dystrobrevin stabilize the sarcolemma membrane by forming a multi-protein complex called dystrophin-associated glycoprotein complex (DAGC) that is destabilized in DMD. Dystrobrevin has two major isoforms, alpha and beta, with tissue-specific expression patterns. Here, we characterize the CT domain of dystrophin and its interactions with the two dystrobrevin isoforms. We show that the CT domain is non-globular and shows reversible urea denaturation as well as thermal denaturation. It interacts with dystrobrevin isoforms differentially, with differences in binding affinity and the mode of interaction. We further show that the amino acid differences in the C-terminal region of dystrobrevin isoforms contribute to these differences. These results have implications for the stability of DAGC in different tissues and explain the differing symptoms associated with DMD patients affecting organs beyond the skeletal muscles.

中文翻译：

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抗肌萎缩蛋白 C 末端结构域的生物物理特征：抗肌萎缩蛋白与 dystrobrevin 亚型的相互作用不同。


杜氏肌营养不良症 （DMD） 基因编码抗肌萎缩蛋白，这是一种大型多结构域蛋白。它的非功能性会导致肌营养不良蛋白病，如 DMD 和贝克尔肌营养不良症 （BMD），目前尚无治愈方法。一些针对特定突变的疗法可以延长患者的寿命，尽管疗效有限且成本高昂，这强调了更通用治疗的需求。抗肌萎缩蛋白结构复杂，结构域知之甚少，并且在不同组织中存在具有不同表达模式的多种亚型，这给治疗开发带来了挑战。抗肌萎缩蛋白的 C 端 （CT） 结构域在其结构-功能方面知之甚少，尽管它已被证明通过与另一种胞质蛋白 dystrobrevin 相互作用来发挥重要的功能作用。抗肌萎缩蛋白和肌萎缩蛋白通过形成一种称为抗肌萎缩蛋白相关糖蛋白复合物 （DAGC） 的多蛋白复合物来稳定肌膜，该复合物在 DMD 中不稳定。Dystrobrevin 有两种主要的亚型，α 和 β，具有组织特异性表达模式。在这里，我们表征了抗肌萎缩蛋白的 CT 结构域及其与两种 dystrobrevin 亚型的相互作用。我们表明 CT 结构域是非球状的，并显示可逆尿素变性以及热变性。它与 dystrobrevin 亚型相互作用不同，结合亲和力和相互作用模式不同。我们进一步表明，dystrobrevin 亚型的 C 末端区域的氨基酸差异导致了这些差异。这些结果对 DAGC 在不同组织中的稳定性有影响，并解释了与 DMD 患者影响骨骼肌以外器官相关的不同症状。