Proteins and synthetic polymers that undergo aqueous phase transitions mediate self-assembly in nature and in man-made material systems. Yet little is known about how the phase behaviour of a protein is encoded in its amino acid sequence. Here, by synthesizing intrinsically disordered, repeat proteins to test motifs that we hypothesized would encode phase behaviour, we show that the proteins can be designed to exhibit tunable lower or upper critical solution temperature (LCST and UCST, respectively) transitions in physiological solutions. We also show that mutation of key residues at the repeat level abolishes phase behaviour or encodes an orthogonal transition. Furthermore, we provide heuristics to identify, at the proteome level, proteins that might exhibit phase behaviour and to design novel protein polymers consisting of biologically active peptide repeats that exhibit LCST or UCST transitions. These findings set the foundation for the prediction and encoding of phase behaviour at the sequence level.
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F.G.Q. thanks K. Zhu for his assistance with the preparation of Fig. 4d. This work was funded by the NIH through grant # GM061232 to A.C. and by the NSF through the Research Triangle MRSEC (NSF DMR-11-21107).
The authors hold US patent no. 8,470,967 that covers many of the peptide sequences described in this Article.
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Quiroz, F., Chilkoti, A. Sequence heuristics to encode phase behaviour in intrinsically disordered protein polymers. Nature Mater 14, 1164–1171 (2015). https://doi.org/10.1038/nmat4418
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