Polymorphism of Lysozyme Condensates

Abstract

Protein condensates play essential roles in physiological processes and pathological conditions. Recently discovered mesoscopic protein-rich clusters may act as crucial precursors for the nucleation of ordered protein solids, such as crystals, sickle hemoglobin polymers, and amyloid fibrils. These clusters challenge settled paradigms of protein condensation as the constituent protein molecules present features characteristic of both partially misfolded and native proteins. Here we employ the antimicrobial enzyme lysozyme and examine the similarities between mesoscopic clusters, amyloid structures, and disordered aggregates consisting of chemically modified protein. We show that the mesoscopic clusters are distinct from the other two classes of aggregates. Whereas cluster formation and amyloid oligomerization are both reversible, aggregation triggered by reduction of the intramolecular S-S bonds is permanent. In contrast to the amyloid structures, protein molecules in the clusters retain their enzymatic activity. Furthermore, an essential feature of the mesoscopic clusters is their constant radius of less than 50 nm. The amyloid and disordered aggregates are significantly larger and rapidly grow. These findings demonstrate that the clusters are a product of limited protein structural flexibility. In view of the role of the clusters in the nucleation of ordered protein solids, our results suggest that fine-tuning the degree of protein conformational stability is a powerful tool to control and direct the pathways of protein condensation.

Mesoscopic Liquid Clusters Represent a Distinct Condensate of Mutant p53

“…38,51,52 The cluster size is determined by the balance between the lifetime of the misassembled oligomers and their rate of outward diffusion from the cluster core and is, hence, independent of the protein concentration and steady in time. 51,53 By contrast, the amount of protein captured in the clusters, and the related number of clusters and cluster population volume, increases exponentially with the protein concentration as a consequence of the thermodynamic equilibrium between the clusters and the bulk solution. 37,51,53 The mesoscopic clusters of both R248Q and wild type p53 53 appear to remarkably well comply with the predictions of this model.…”

“…51,53 By contrast, the amount of protein captured in the clusters, and the related number of clusters and cluster population volume, increases exponentially with the protein concentration as a consequence of the thermodynamic equilibrium between the clusters and the bulk solution. 37,51,53 The mesoscopic clusters of both R248Q and wild type p53 53 appear to remarkably well comply with the predictions of this model.…”

Weakly-bound Dimers that Underlie the Crystal Nucleation Precursors in Lysozyme Solutions

“…Furthermore, the data presented here provide no evidence regarding the structure of the detected weakly-bound dimers or their spatial distribution throughout the solution volume. A series of published results, however, demonstrates that native lysozyme molecules do not dimerize (42) and partial unfolding that exposes to the solution the hydrophobic interface between the constituent structural domains drives the unfolded molecules into mesoscopic protein-rich clusters (38)(39)(40)44). Collectively, the published and present results suggest that the dimers consist of partially unfolded lysozyme molecules bound by hydrophobic contacts between their interdomain interfaces, as illustrated in Scheme 1A, and assemble into mesoscopic clusters, Scheme 1B (32).…”

“…Their diameters are of order 100 nm (22,26,34,35) and each cluster contains 10 4 -10 5 protein molecules (26, 32-34, 36, 37). With lysozyme, a robust protein used as a model in several biophysics fields, cluster formation is reversible and the clusters exchange protein with the host solution (33,(37)(38)(39)(40). Remarkably, the responses of the characteristic cluster size and phase volume to variations of the ionic strength, pH, and additive concentration are decoupled and the cluster size is independent of protein concentration, solution ionic strength, and pH (39,40).…”

The Alkanes with Maximum Wiener Polarity Index

“…Examples, which indicate the chemical applicability of W p , can be found in the references. [3][4][5][6][7][8][9] The index W p has attracted a considerable attention from researchers in the last decade, see for example the recent papers [10][11][12][13][14][15][16][17] and related references listed therein.…”