Tie-Line Analysis Reveals Interactions Driving Heteromolecular Condensate Formation

Phase separation of biomolecules gives rise to membraneless organelles that contribute the spatiotemporal organization cell. In most cases, such biomolecular condensates contain multiple components, but manner in which interactions between components control stability have remained challenging elucidate. Here, we develop an approach determine tie-line gradients ternary phase-separation systems based on measurements dilute phase concentration only one component. We show sign gradient is related cross-interaction energy polymers system and discriminates associative segregative separation. Using this approach, study interaction protein fused sarcoma (FUS) polyethylene glycol (PEG) polymer chains measure positive gradients. Our results PEG drives through with FUS, other than acting as inert crowder. further poly(A) ribonucleic acid (RNA) (3.0±0.5 kDa [kilodalton]) G3BP1, using a reporter for stoichiometry condensate, G3BP1-to-poly(A) RNA molar ratio 1∶4 dense phase. framework measuring opens up route characterization types compositions systems.Received 31 May 2022Revised 24 October 2022Accepted 1 December 2022DOI:https://doi.org/10.1103/PhysRevX.12.041038Published by American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution work must maintain attribution author(s) published article’s title, journal citation, DOI.Published SocietyPhysics Subject Headings (PhySH)Research AreasLiquid-liquid transitionProtein-protein interactionsTechniquesConfocal imagingBiological Physics