Atomic resolution map of the solvent interactions driving SOD1 unfolding in CAPRIN1 condensates

• 成果类型: Article
• 署名作者: Ahmed, Rashik; Liang, Mingyang; Hudson, Rhea P.; Rangadurai, Atul K.; Huang, Shuya Kate; Forman-Kay, Julie D.; Kay, Lewis E.
• 署名单位: University of Toronto; University of Toronto; University of Toronto; University of Toronto; Hospital for Sick Children (SickKids)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9509
• DOI: 10.1073/pnas.2408554121
• 发表日期: 2024-08-27
• 关键词: molecular-weight proteins; liquid phase-separation; superoxide-dismutase; nmr-spectroscopy; stress granules; TRANSITION; maturation; STABILITY; copper; translation

摘要

Biomolecules can be sequestered into membrane- less compartments, referred to as biomolecular condensates. Experimental and computational methods have helped define the physical- chemical properties of condensates. Less is known about how the high macromolecule concentrations in condensed phases contribute solvent interactions that can remodel the free- energy landscape of other condensate- resident proteins, altering thermally accessible conformations and, in turn, modulating function. Here, we use solution NMR spectroscopy to obtain atomic resolution insights into the interactions between the immature form of superoxide dismutase 1 (SOD1), which can mislocalize and aggregate in stress granules, and the RNA- binding protein CAPRIN1, a component of stress granules. NMR studies of CAPRIN1:SOD1 interactions, focused on condensates, establish that CAPRIN1 shifts the SOD1 folding equilibrium toward the unfolded state through preferential interactions with the unfolded ensemble, with little change to the structure of the folded conformation. Key contacts between CAPRIN1 and the H80- H120 region of unfolded SOD1 are identified, as well as SOD1 interaction sites near both the arginine- rich and aromatic- rich regions of CAPRIN1. Unfolding of immature SOD1 in the CAPRIN1 condensed phase is shown to be coupled to aggregation, while a more stable zinc- bound, dimeric form of SOD1 is less susceptible to unfolding when solvated by CAPRIN1. Our work underscores the impact of the condensate solvent environment on the conformational states of resident proteins and supports the hypothesis that ALS mutations that decrease metal binding or dimerization function as drivers of aggregation in condensates.