Molecular crowding facilitates assembly of spidroin-like proteins through phase separation

Laura Lemetti, Sami Pekka Hirvonen, Dmitrii Fedorov, Piotr Batys, Maria Sammalkorpi, Heikki Tenhu, Markus B. Linder*, A. Sesilja Aranko

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

14 Citations (Scopus)
172 Downloads (Pure)


Gaining insights into the processes that transform dispersed biopolymers into well-ordered structures, such as soluble spidroin-proteins to spider silk threads, is essential for attempts to understand their biological function and to mimic their unique properties. One of these processes is liquid-liquid phase separation, which can act as an intermediate step for molecular assembly. We have shown that a self-coacervation step that occurs at a very high protein concentration (>200 gl−1) is crucial for the fiber assembly of an engineered triblock silk-like molecule. In this study, we demonstrate that the addition of a crowding agent lowers the concentration at which coacervation occurs by almost two orders of magnitude. Coacervates induced by addition of a crowding agent are functional in terms of fiber formation, and the crowding agent appears to affect the process solely by increasing the effective concentration of the protein. Furthermore, induction at lower concentrations allows us to study the thermodynamics of the system, which provides insights into the coacervation mechanism. We suggest that this approach will be valuable for studies of biological coacervating systems in general.

Original languageEnglish
Pages (from-to)539-546
Number of pages8
JournalEuropean Polymer Journal
Publication statusPublished - Mar 2019
MoE publication typeA1 Journal article-refereed


  • Biopolymer
  • Coacervation
  • FRAP
  • Fusion protein
  • Isothermal titration calorimetry
  • Liquid-liquid phase separation
  • Molecular crowding
  • Self-coacervation
  • Spidroin


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