Solutes unmask differences in clustering versus phase separation of FET proteins

• Published in: Nature communications Vol. 15; no. 1; p. 4408
• Main Authors: Kar, Mrityunjoy, Vogel, Laura T., Chauhan, Gaurav, Felekyan, Suren, Ausserwöger, Hannes, Welsh, Timothy J., Dar, Furqan, Kamath, Anjana R., Knowles, Tuomas P. J., Hyman, Anthony A., Seidel, Claus A. M., Pappu, Rohit V.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.05.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/125; 631/1647/328/1978; 631/45/612/1245; 631/57/2269; Chlorides; Chlorides - chemistry; Clustering; Clusters; Condensates; FLI-1 protein; Glutamic Acid - chemistry; Humanities and Social Sciences; Humans; Macromolecules; multidisciplinary; Percolation; Phase Separation; Phase Transition; Phase transitions; Proteins; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - metabolism; Science; Science (multidisciplinary); Solutes; Solutions; Viscoelasticity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-48775-3

Phase separation and percolation contribute to phase transitions of multivalent macromolecules. Contributions of percolation are evident through the viscoelasticity of condensates and through the formation of heterogeneous distributions of nano- and mesoscale pre-percolation clusters in sub-saturated solutions. Here, we show that clusters formed in sub-saturated solutions of FET (FUS-EWSR1-TAF15) proteins are affected differently by glutamate versus chloride. These differences on the nanoscale, gleaned using a suite of methods deployed across a wide range of protein concentrations, are prevalent and can be unmasked even though the driving forces for phase separation remain unchanged in glutamate versus chloride. Strikingly, differences in anion-mediated interactions that drive clustering saturate on the micron-scale. Beyond this length scale the system separates into coexisting phases. Overall, we find that sequence-encoded interactions, mediated by solution components, make synergistic and distinct contributions to the formation of pre-percolation clusters in sub-saturated solutions, and to the driving forces for phase separation. Biomolecular condensates form via phase separation of multivalent macromolecules. Phase separation is governed by solubility whereas multivalence drives percolation, also known as gelation. The authors in this work identify the distinct energy and length scales that influence phase separation versus percolation.