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: England Nature Publishing Group 23.05.2024; Nature Portfolio
• Subjects: Chlorides; Chlorides - chemistry; Clustering; Clusters; Condensates; FLI-1 protein; Glutamic Acid - chemistry; Humans; Macromolecules; Percolation; Phase Separation; Phase Transition; Phase transitions; Proteins; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - metabolism; 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.