Year: 2021
Type: article
Abstract: Low-complexity (LC) domains found in RNA-binding proteins associated with liquid-liquid phase separation form a specific class of intrinsically disordered domains. LC domains have distinct amino acid compositions; they are enriched in polar amino acids (especially Ser and Gly), and feature conserved patterns of aromatic residues. in many cases, these disordered LC domains are necessary and sufficient for driving phase separation. Liquid condensates are believed to be the result of multivalent weak interactions between multiple interacting motifs in LC domains, including electrostatic, cation-pi and pi-pi interactions. Yet, the relative contribution of these interactions to phase separation is largely unknown. Here we investigate the pressure- and temperature-induced conformational changes associated with the low complexity domain of hnRNP A1, an RNA-binding protein able to phase separate in response to cellular stress. Solution NMR spectra of the hnRNP A1 low-complexity domain fused with protein-G B1 domain were collected from 1 to 2,500 bar and from 268 K to 290 K. While the GB1 domain shows the typical pressure-induced and cold temperature-induced unfolding expected for small globular domains, the low-complexity domain of hnRNP A1 exhibits unusual pressure and temperature dependences. We observed that the low-complexity domain is pressure sensitive, undergoing a major conformational transition within the prescribed pressure range. Remarkably, this transition has the inverse temperature dependence of a typical folding-unfolding transition. Our results suggest the presence of a low-lying extended, and fully solvated state(s) of the low-complexity domain that may play a role in phase separation. This study highlights the exquisite sensitivity of solution NMR spectroscopy to observe subtle conformational changes and illustrates how pressure perturbation can be used to determine the properties of metastable conformational ensembles.
Source: Biophysical Journal
Institutions: Case Western Reserve University, Iowa State University
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W3132432948