Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 116, Issue 39, Pages 19474-19483Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1907849116
Keywords
liquid-liquid phase separation; macromolecular regulator; partition coefficient; membraneless organelles
Categories
Funding
- NIH [GM118091]
Ask authors/readers for more resources
Membraneless organelles, corresponding to the droplet phase upon liquid-liquid phase separation (LLPS) of protein or protein-RNA mixtures, mediate myriad cellular functions. Cells use a variety of biochemical signals such as expression level and posttranslational modification to regulate droplet formation and dissolution, but the physical basis of the regulatory mechanisms remains ill-defined and quantitative assessment of the effects is largely lacking. Our computational study predicted that the strength of attraction by droplet-forming proteins dictates whether and how macromolecular regulators promote or suppress LLPS. We experimentally tested this prediction, using the pentamers of SH3 domains and proline-rich motifs (SH3(5) and PRM5) as droplet-forming proteins. Determination of the changes in phase boundary and the partition coefficients in the droplet phase over a wide range of regulator concentrations yielded both a quantitative measure and a mechanistic understanding of the regulatory effects. Three archetypical classes of regulatory effects were observed. Ficoll 70 at high concentrations indirectly promoted SH3(5)-PRM5 LLPS, by taking up volume in the bulk phase and thereby displacing SH3(5) and PRM5 into the droplet phase. Lysozyme had a moderate partition coefficient and suppressed LLPS by substituting weaker attraction with SH3(5) for the stronger SH3(5)-PRM5 attraction in the droplet phase. By forming even stronger attraction with PRM5, heparin at low concentrations partitioned heavily into the droplet phase and promoted LLPS. These characteristics were recapitulated by computational results of patchy particle models, validating the identification of the 3 classes of macromolecular regulators as volume-exclusion promotors, weak-attraction suppressors, and strong-attraction promotors.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available