Direct observation of structure and dynamics during phase separation of an elastomeric protein.

Autor: Reichheld SE; Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON, Canada, M5G 0A4., Muiznieks LD; Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON, Canada, M5G 0A4., Keeley FW; Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON, Canada, M5G 0A4.; Department of Biochemistry, University of Toronto, Toronto, ON, Canada, M5S 1A8., Sharpe S; Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON, Canada, M5G 0A4; ssharpe@sickkids.ca.; Department of Biochemistry, University of Toronto, Toronto, ON, Canada, M5S 1A8.
Jazyk: angličtina
Zdroj: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2017 May 30; Vol. 114 (22), pp. E4408-E4415. Date of Electronic Publication: 2017 May 15.
DOI: 10.1073/pnas.1701877114
Abstrakt: Despite its growing importance in biology and in biomaterials development, liquid-liquid phase separation of proteins remains poorly understood. In particular, the molecular mechanisms underlying simple coacervation of proteins, such as the extracellular matrix protein elastin, have not been reported. Coacervation of the elastin monomer, tropoelastin, in response to heat and salt is a critical step in the assembly of elastic fibers in vivo, preceding chemical cross-linking. Elastin-like polypeptides (ELPs) derived from the tropoelastin sequence have been shown to undergo a similar phase separation, allowing formation of biomaterials that closely mimic the material properties of native elastin. We have used NMR spectroscopy to obtain site-specific structure and dynamics of a self-assembling elastin-like polypeptide along its entire self-assembly pathway, from monomer through coacervation and into a cross-linked elastic material. Our data reveal that elastin-like hydrophobic domains are composed of transient β-turns in a highly dynamic and disordered chain, and that this disorder is retained both after phase separation and in elastic materials. Cross-linking domains are also highly disordered in monomeric and coacervated ELP 3 and form stable helices only after chemical cross-linking. Detailed structural analysis combined with dynamic measurements from NMR relaxation and diffusion data provides direct evidence for an entropy-driven mechanism of simple coacervation of a protein in which transient and nonspecific intermolecular hydrophobic contacts are formed by disordered chains, whereas bulk water and salt are excluded.
Competing Interests: The authors declare no conflict of interest.
Databáze: MEDLINE
Externí odkaz: