Programming molecular self-assembly of intrinsically disordered proteins containing sequences of low complexity


Dynamic protein-rich intracellular structures that contain phase-separated intrinsically disordered proteins (IDPs) composed of sequences of low complexity (SLC) have been shown to serve a variety of important cellular functions, which include signalling, compartmentalization and stabilization. However, our understanding of these structures and our ability to synthesize models of them have been limited. We present design rules for IDPs possessing SLCs that phase separate into diverse assemblies within droplet microenvironments. Using theoretical analyses, we interpret the phase behaviour of archetypal IDP sequences and demonstrate the rational design of a vast library of multicomponent protein-rich structures that ranges from uniform nano-, meso- and microscale puncta (distinct protein droplets) to multilayered orthogonally phase-separated granular structures. The ability to predict and program IDP-rich assemblies in this fashion offers new insights into (1) genetic-to-molecular-to-macroscale relationships that encode hierarchical IDP assemblies, (2) design rules of such assemblies in cell biology and (3) molecular-level engineering of self-assembled recombinant IDP-rich materials.

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Figure 1: Programming of artificial liquid coacervates from ELPs.
Figure 2: Reversible formation of ELP coacervates inside droplets by spinodal decomposition and resolubilzation.
Figure 3: Multicomponent solutions of ELPs enable the formation of layered and mixed coacervates.
Figure 4: Amphiphilic proteins kinetically arrest coalescence of ELPs during phase separation to produce uniform nano-, meso- and microscale puncta.


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We are grateful for support from the National Science Foundation (NSF) Research Triangle MRSEC (DMR-1121107), Pratt–Gardner Fellowship (J.R.S.), Medtronic Inc. Fellowship in Biomedical Engineering (J.R.S.) and the NSF Graduate Research Fellowship Program (DGF1106401) (J.R.S.). A.C. acknowledges the support of the National Institutes of Health (NIH) though grants R01-GM61232, R01-EB000188 and R01-EB007205. M.R. acknowledges financial support from the NSF under grants DMR-1309892 and DMR-1436201, the NIH under grants P01-HL108808 and 1UH2HL123645, and the Cystic Fibrosis Foundation. We thank J. McDaniel, S. MacEwan and J. Genzer for their helpful discussions and for providing some of the plasmids containing genes that encode the ELPs used in this study. We also thank the Duke Light Core Microscopy Facility for fruitful discussions and help with confocal microscopy experiments.

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J.R.S carried out experiments, protein design, expression and purification, fluorescence imaging, light scattering measurements, data analysis and manuscript preparation. N.J.C. carried out experiments, light scattering measurements, microfluidic device fabrication, data analysis, manuscript preparation and provided overall intellectual guidance. M.R. provided theoretical guidance, design of experiments, phase-diagram measurements, data interpretation and manuscript editing. A.C. provided the plasmids for protein constructs, and guidance on ELP production, ELP phase behaviour and manuscript editing. G.P.L. directed all the experiments and measurements, provided intellectual guidance, approved final edits to the manuscript and was principal investigator of the primary supporting grant. All the authors discussed the results and commented on the manuscript.

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Correspondence to Nick J. Carroll or Gabriel P. López.

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The authors declare no competing financial interests.

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Simon, J., Carroll, N., Rubinstein, M. et al. Programming molecular self-assembly of intrinsically disordered proteins containing sequences of low complexity. Nature Chem 9, 509–515 (2017).

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