Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205.
Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218.
Proc Natl Acad Sci U S A. 2023 May 9;120(19):e2215068120. doi: 10.1073/pnas.2215068120. Epub 2023 May 1.
Poly(ADP-ribose) (PAR) is a homopolymer of adenosine diphosphate ribose that is added to proteins as a posttranslational modification to regulate numerous cellular processes. PAR also serves as a scaffold for protein binding in macromolecular complexes, including biomolecular condensates. It remains unclear how PAR achieves specific molecular recognition. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) to evaluate PAR flexibility under different cation conditions. We demonstrate that, compared to RNA and DNA, PAR has a longer persistence length and undergoes a sharper transition from extended to compact states in physiologically relevant concentrations of various cations (Na, Mg, Ca, and spermine). We show that the degree of PAR compaction depends on the concentration and valency of cations. Furthermore, the intrinsically disordered protein FUS also served as a macromolecular cation to compact PAR. Taken together, our study reveals the inherent stiffness of PAR molecules, which undergo switch-like compaction in response to cation binding. This study indicates that a cationic environment may drive recognition specificity of PAR.
聚（ADP-核糖）（PAR）是一种二磷酸腺苷核糖的同聚物，作为一种翻译后修饰添加到蛋白质中，以调节许多细胞过程。PAR 还可以作为蛋白质结合的支架，存在于大分子复合物中，包括生物分子凝聚物。目前尚不清楚 PAR 如何实现特定的分子识别。在这里，我们使用单分子荧光共振能量转移（smFRET）来评估不同阳离子条件下 PAR 的灵活性。我们证明，与 RNA 和 DNA 相比，PAR 具有更长的持久长度，并在生理相关浓度的各种阳离子（Na、Mg、Ca 和 spermine）中经历从伸展到紧凑状态的更急剧转变。我们表明，PAR 的紧凑程度取决于阳离子的浓度和价态。此外，固有无序蛋白 FUS 也作为一种大分子阳离子来使 PAR 紧凑。总之，我们的研究揭示了 PAR 分子的固有刚性，它们在响应阳离子结合时发生类似开关的紧凑化。这项研究表明，阳离子环境可能会促进 PAR 的识别特异性。
