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The protein p53 is a crucial tumor suppressor, often called “the guardian of the genome”; however, mutations transform p53 into a powerful cancer promoter. The oncogenic capacity of mutant p53 has been ascribed to enhanced propensity to fibrillize and recruit other cancer fighting proteins in the fibrils, yet the pathways of fibril nucleation and growth remain obscure. Here, we combine immunofluorescence three-dimensional confocal microscopy of human breast cancer cells with light scattering and transmission electron microscopy of solutions of the purified protein and molecular simulations to illuminate the mechanisms of phase transformations across multiple length scales, from cellular to molecular. We report that the p53 mutant R248Q (R, arginine; Q, glutamine) forms, both in cancer cells and in solutions, a condensate with unique properties, mesoscopic protein-rich clusters. The clusters dramatically diverge from other protein condensates. The cluster sizes are decoupled from the total cluster population volume and independent of the p53 concentration and the solution concentration at equilibrium with the clusters varies. We demonstrate that the clusters carry out a crucial biological function: they host and facilitate the nucleation of amyloid fibrils. We demonstrate that the p53 clusters are driven by structural destabilization of the core domain and not by interactions of its extensive unstructured region, in contradistinction to the dense liquids typical of disordered and partially disordered proteins. Two-step nucleation of mutant p53 amyloids suggests means to control fibrillization and the associated pathologies through modifying the cluster characteristics. Our findings exemplify interactions between distinct protein phases that activate complex physicochemical mechanisms operating in biological systems.
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Insights into the solubility of γD‐crystallin from multiscale atomistic simulations
Abstract The molecular basis underlying the rich phase behavior of globular proteins remains poorly understood. We use atomistic multiscale molecular simulations to model the solution‐state conformational dynamics and interprotein interactions of D‐crystallin and its P23T‐R36S mutant, which drastically limits the protein solubility, at both infinite dilution and at a concentration where the mutant fluid phase and crystalline phase coexist. We find that while the mutant conserves the protein fold, changes to the surface exposure of residues in the neighborhood of residue‐36 enhance protein–protein interactions and develop specific protein–protein contacts found in the protein crystal lattice.
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- Award ID(s):
- 2011967
- PAR ID:
- 10413943
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Computational Chemistry
- Volume:
- 44
- Issue:
- 19
- ISSN:
- 0192-8651
- Page Range / eLocation ID:
- p. 1658-1666
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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