Dynamic structural changes and thermodynamics in phase separation processes of an intrinsically disordered–ordered protein model

Abstract

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.