Zhu Longchen, Pan Yifei, Hua Ziyi, Liu Yu, Zhang Xin
Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Hangzhou 310030, P. R. China.
CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China.
J Am Chem Soc. 2024 May 22;146(20):14307-14317. doi: 10.1021/jacs.4c04036. Epub 2024 May 9.
Biomolecules such as proteins and RNA could organize to form condensates with distinct microenvironments through liquid-liquid phase separation (LLPS). Recent works have demonstrated that the microenvironment of biomolecular condensates plays a crucial role in mediating biological activities, such as the partition of biomolecules, and the subphase organization of the multiphasic condensates. Ions could influence the phase transition point of LLPS, following the Hofmeister series. However, the ion-specific effect on the microenvironment of biomolecular condensates remains unknown. In this study, we utilized fluorescence lifetime imaging microscopy (FLIM), fluorescence recovery after photobleaching (FRAP), and microrheology techniques to investigate the ion effect on the microenvironment of condensates. We found that ions significantly affect the microenvironment of biomolecular condensates: salting-in ions increase micropolarity and reduce the microviscosity of the condensate, while salting-out ions induce opposing effects. Furthermore, we manipulate the miscibility and multilayering behavior of condensates through ion-specific effects. In summary, our work provides the first quantitative survey of the microenvironment of protein condensates in the presence of ions from the Hofmeister series, demonstrating how ions impact micropolarity, microviscosity, and viscoelasticity of condensates. Our results bear implications on how membrane-less organelles would exhibit varying microenvironments in the presence of continuously changing cellular conditions.
蛋白质和RNA等生物分子可通过液-液相分离（LLPS）组织形成具有独特微环境的凝聚物。最近的研究表明，生物分子凝聚物的微环境在介导生物活性方面起着关键作用，例如生物分子的分配以及多相凝聚物的亚相组织。离子可按照霍夫迈斯特序列影响LLPS的相变点。然而，离子对生物分子凝聚物微环境的特异性影响仍然未知。在本研究中，我们利用荧光寿命成像显微镜（FLIM）、光漂白后荧光恢复（FRAP）和微观流变学技术来研究离子对凝聚物微环境的影响。我们发现离子会显著影响生物分子凝聚物的微环境：盐溶离子会增加微极性并降低凝聚物的微粘度，而盐析离子则会产生相反的效果。此外，我们通过离子特异性效应来操控凝聚物的混溶性和多层行为。总之，我们的工作首次对存在霍夫迈斯特序列离子时蛋白质凝聚物的微环境进行了定量研究，展示了离子如何影响凝聚物的微极性、微粘度和粘弹性。我们的结果对于无膜细胞器在细胞条件不断变化的情况下如何呈现不同的微环境具有启示意义。
