Biomolecular condensates are non-stoichiometric assemblies that are characterized by their capacity to spatially concentrate biomolecules and play a key role in cellular organization. Proteins that drive the formation of biomolecular condensates frequently contain oligomerization domains and intrinsically disordered regions (IDRs), both of which can contribute multivalent interactions that drive higher-order assembly. Our understanding of the relative and temporal contribution of oligomerization domains and IDRs to the material properties of in vivo biomolecular condensates is limited. Similarly, the spatial and temporal dependence of protein oligomeric state inside condensates has been largely unexplored in vivo. In this study, we combined quantitative microscopy with number and brightness analysis to investigate the aging, material properties, and protein oligomeric state of biomolecular condensates in vivo. Our work is focused on condensates formed by AUXIN RESPONSE FACTOR 19 (ARF19), a transcription factor integral to the auxin signaling pathway in plants. ARF19 contains a large central glutamine-rich IDR and a C-terminal Phox Bem1 (PB1) oligomerization domain and forms cytoplasmic condensates. Our results reveal that the IDR amino acid composition can influence the morphology and material properties of ARF19 condensates. In contrast the distribution of oligomeric species within condensates appears insensitive to the IDR composition. In addition, we identified a relationship between the abundance of higher- and lower-order oligomers within individual condensates and their apparent fluidity. IDR amino acid composition affects condensate morphology and material properties. In ARF condensates, altering the amino acid composition of the IDR did not greatly affect the oligomeric state of proteins within the condensate.

中文翻译：

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通过数量和亮度分析测量细胞内凝聚物形态、动力学和寡聚化的序列决定因素


生物分子凝聚体是非化学计量的组装体，其特征在于其能够在空间上集中生物分子并在细胞组织中发挥关键作用。驱动生物分子缩合物形成的蛋白质通常包含寡聚结构域和本质无序区域 (IDR)，这两者都可以促进驱动高阶组装的多价相互作用。我们对寡聚结构域和 IDR 对体内生物分子凝聚物材料特性的相对和时间贡献的理解是有限的。类似地，体内蛋白质寡聚状态的空间和时间依赖性在很大程度上尚未得到探索。在这项研究中，我们将定量显微镜与数量和亮度分析相结合，研究体内生物分子凝聚物的老化、材料特性和蛋白质寡聚状态。我们的工作重点是生长素响应因子 19 (ARF19) 形成的缩合物，生长素响应因子 19 是植物生长素信号通路中不可或缺的转录因子。 ARF19 含有一个大的中央富含谷氨酰胺的 IDR 和一个 C 端 Phox Bem1 (PB1) 寡聚结构域，并形成细胞质凝聚物。我们的结果表明，IDR 氨基酸组成可以影响 ARF19 缩合物的形态和材料性能。相比之下，冷凝物中低聚物的分布似乎对 IDR 成分不敏感。此外，我们还确定了单个冷凝物中高阶和低阶低聚物的丰度与其表观流动性之间的关系。 IDR 氨基酸组成影响冷凝物形态和材料性能。 在 ARF 凝聚物中，改变 IDR 的氨基酸组成并不会极大地影响凝聚物内蛋白质的寡聚状态。