Dynamic Structural Changes and Thermodynamics in Phase Separation Processes of an Intrinsically Disordered–Ordered Protein Model

• Published in: Angewandte Chemie International Edition 2022-01, Vol.61 (3), p.e202112738-n/a
• Main Authors: Lüdeke, Steffen, Lohner, Philipp, Stühn, Lara G., Betschart, Martin U., Huber, Matthias C., Schreiber, Andreas, Schiller, Stefan M.
• Format: Article
• Language: English
• Subjects: Assembly; Circular Dichroism; Coacervation; Dichroism; Elastin; elastin-like proteins; Humans; intrinsically disordered proteins; Intrinsically Disordered Proteins - chemistry; Intrinsically Disordered Proteins - metabolism; Liquid phases; matrix least-squares global fitting; Models, Molecular; Peptides - chemistry; Peptides - metabolism; Phase separation; Phase transitions; Polypeptides; protein assembly; Protein Conformation; Proteins; Separation processes; Smart materials; Thermodynamics
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202112738

Elastin‐like proteins (ELPs) are biologically important proteins and models for intrinsically disordered proteins (IDPs) and dynamic structural transitions associated with coacervates and liquid–liquid phase transitions. However, the conformational status below and above coacervation temperature and its role in the phase separation process is still elusive. Employing matrix least‐squares global Boltzmann fitting of the circular dichroism spectra of the ELPs (VPGVG)20, (VPGVG)40, and (VPGVG)60, we found that coacervation occurs sharply when a certain number of repeat units has acquired β‐turn conformation (in our sequence setting a threshold of approx. 20 repeat units). The character of the differential scattering of the coacervate suspensions indicated that this fraction of β‐turn structure is still retained after polypeptide assembly. Such conformational thresholds may also have a role in other protein assembly processes with implications for the design of protein‐based smart materials. Elastin‐like proteins (ELPs) undergo reversible coacervation above a certain transition temperature. The thermodynamic analysis of temperature‐dependent circular dichroism of ELPs of different chain‐length revealed that this is preceded by a step‐by‐step increase of β‐turn structure. When a certain threshold is reached, phase separation occurs. The conformational ratio in the assembled protein particles still corresponds to this threshold.